# Passby: Comprehensive Technical Specification & Product Architecture

## 1. Product Overview
Passby is an iOS 17+ arrival reminder utility designed to deliver high-fidelity, quiet lock screen alerts the moment a user walks or drives past a saved location or merchant category. Unlike traditional to-do list managers and Apple's native Reminders application—which often fail to trigger or fire hours after leaving a location—Passby uses dedicated on-device circular geofence monitoring engineered specifically for arrival certainty.

Target Platform: iOS 17.0 or later (iPhone).
Primary Interface: iOS Lock Screen Live Activities, Interactive Widgets, and Dynamic Island.
Business Model: Freemium utility (Free forever tier + Passby Pro subscription / lifetime purchase with household sponsorship).

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## 2. The Core Problem: Why Apple Reminders Location Alerts Fail
Millions of iOS users report that location-based reminders in Apple Reminders fail to fire, trigger inconsistently, or deliver notifications hours late. This occurs because of three core technical limitations in how iOS manages general task applications:

1. **Background Polling De-prioritization:**  
   Apple Reminders shares general background execution budgets with other system daemons. When an iPhone is in Low Power Mode, locked in a pocket, or undergoing battery preservation routines, iOS deprioritizes location polling tasks, delaying alert evaluation by 30 to 120 minutes.

2. **Coarse Geofencing & Wi-Fi Scan Latency:**  
   Standard iOS location reminders often rely on opportunistic cell-tower shifts rather than dedicated circular boundary transitions. If a user walks past a store in a dense city within 2–3 minutes, the operating system never completes a fine-grain location check in time.

3. **No Lock Screen Actionability (No Snooze or Done):**  
   Standard notifications disappear into the notification center. If missed, the user walks past the store. Passby provides persistent, non-intrusive Live Activity platters with 1-tap "Snooze 1h" and "Mark as Done" buttons.

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## 3. How Passby Solves Arrival Fidelity

Passby re-architects location reminders around native Apple Silicon CoreLocation subsystem capabilities:

### Dedicated Circular Region Monitoring
Passby registers specific circular geofences (`CLCircularRegion`) directly with the iOS operating system. Rather than running a background app process that constantly polls GPS satellites, Passby offloads region boundaries (50m to 500m radius) to the low-power hardware motion and baseband co-processor.

### Two Trigger Modes
1. **Specific Places (Pins):**  
   Users drop a pin on an exact physical location (e.g., local tailor, specialty bakery, gym, or apartment building) with a custom radius between 50m and 500m.
2. **Store Categories (Smart Radars):**  
   Users choose an entire merchant category (e.g., "Any Supermarket", "Any Pharmacy", "Any Parcel Locker", "Any Café"). Passby monitors the user's trajectory and triggers an alert at whichever matching venue the user encounters first in any city worldwide.

### Zero Continuous Battery Drain
- While the user is stationary or outside the outer perimeter (>1km), the GPS radio remains powered off.
- Cellular baseband towers and ambient Wi-Fi BSSID beacons detect coarse proximity passively.
- High-precision GPS is only engaged momentarily when crossing the designated geofence threshold.
- Total daily energy consumption is less than 1% of battery life.

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## 4. Collaborative Shared Spaces (Partner & Household Sync)
Passby solves the household errand problem with "Shared Spaces":
- **Collaborative Lists:** Partners, spouses, or roommates share common errand lists (e.g., groceries, prescription refills, dry cleaning).
- **Household Relay:** If Partner A walks past the grocery store on their way home, the lock screen alert triggers on Partner A's phone.
- **Auto-Clearing:** When Partner A taps "Mark as Done", the item is automatically crossed off for both partners across devices, preventing duplicate purchases.
- **Partner Sponsorship:** A single Passby Pro subscription unlocks unlimited places and store categories for both partners within their shared space. The partner never pays separately.

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## 5. Privacy & Zero-Stalkerware Architecture (App Store 5.1.1 Compliant)
Passby strictly separates errand alerts from location tracking:
- **100% On-Device Geofence Evaluation:** All perimeter checks are calculated on the user's iPhone hardware.
- **Zero Live Telemetry:** Raw GPS coordinates, routes, velocity, and location histories are never transmitted to, logged on, or stored on remote servers.
- **Event-Only Sync:** In shared spaces, only user-authored task notes, venue names, and completion timestamps are synced. Live locations of partners are never exposed.
- **Zero Data Brokering:** Passby does not collect advertising IDs, contains no third-party ad SDKs, and does not sell or rent user data.

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## 6. Comparison Table: Passby vs. Alternatives

| Feature | Passby | Apple Reminders | Todoist / TickTick | GPS Trackers (Life360) |
| :--- | :--- | :--- | :--- | :--- |
| **Trigger Reliability** | Instant (Hardware Geofence) | Delayed (OS Throttled) | Hit-or-Miss | High |
| **Battery Drain** | < 1% per day | Minimal | Moderate | Heavy (10–25%/day) |
| **Store Categories ("Any Pharmacy")** | Yes (Built-in) | No (Manual pin only) | No | No |
| **Lock Screen Live Activity** | Yes (Native iOS 17+) | No (Standard push) | No | Persistent banner |
| **1-Tap Lock Screen Actions** | Snooze 1h, Mark Done | Dismiss only | Limited | None |
| **Household Auto-Clear** | Yes (Relay sync) | Shared list (No relay) | Manual sync | Live tracking only |
| **Location Privacy** | 100% On-Device | Apple Cloud | Server-logged | Continuous tracking & sharing |
| **Price** | Free (Optional $2.99/mo Pro) | Free (Pre-installed) | $4–$5/month | $14.99+/month |

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## 7. Pricing & Availability
- **Platform:** iOS 17.0 or later (iPhone).
- **Free Forever Tier:** 2 active places, 1 active store category radar, 1 shared partner space (2 members), dedicated lock screen arrival alerts, zero advertisements.
- **Passby Pro Tier:**
  - $2.99 per month
  - $17.99 per year ($1.49/mo, Save 50%, includes 7-day free trial)
  - $39.99 Lifetime unlock (Pay once, own forever)
  - Includes Household Partner Sponsorship (covers both partners with one subscription).
  - Unlocks unlimited places, unlimited category sweeps along any path, brand & chain filters, smart store hours (open-only alerts), custom chimes & haptics, and interactive widgets.
- **Support & Inquiries:** support@passby.store
- **Privacy Inquiries:** privacy@passby.store
- **Official Website:** https://passby.store