How DiscoverPrompt Works
A comprehensive guide to tracker detection.
Continuous Bluetooth Scanning
When you start a scan, DiscoverPrompt activates your device's Bluetooth receiver to detect all nearby BLE (Bluetooth Low Energy) devices. This includes tracking devices like AirTags, Tiles, Samsung SmartTags, as well as everyday devices like headphones, fitness bands, and smart watches.
Signal Strength Analysis
We measure each device's RSSI (Received Signal Strength Indicator) to estimate its distance from you. Devices are categorized into proximity bands: close (0-3 meters), medium (3-10 meters), and far (10-20 meters). The radar visualization shows where devices are located around you.
Persistence Tracking
The key to detecting trackers is persistence. Normal environmental devices (like a neighbor's speaker or a passing pedestrian's phone) appear briefly and then disappear. A tracking device hidden in your belongings or vehicle will remain consistently visible across time and location changes.
Threat Detection
When a device remains in close proximity for 8 minutes or more, DiscoverPrompt triggers an alert. This threshold is calibrated to minimize false positives while catching real threats. The device color changes from yellow (nearby) to orange (warning) to red (potential threat) based on persistence duration.
Take Action
When alerted, you can check your belongings, vehicle, or person for hidden devices. Common hiding spots include bags, car wheel wells, jacket pockets, and any area someone could have briefly accessed. If you find a device, document it and contact local authorities if you believe you're being stalked.
Technical Details
RSSI to Distance Calculation
We use the log-distance path loss model to estimate device distance:
distance = 10 ^ ((txPower - RSSI) / (10 × n))Where txPower is the reference signal strength at 1 meter (~-59 dBm) and n is the path loss exponent (typically 2.0 for indoor environments).
Device Identification
BLE devices broadcast advertisement packets containing a unique identifier. Some tracking devices rotate their IDs to avoid detection, but we track behavioral patterns (signal strength consistency, persistence duration) rather than relying solely on static identifiers.
Web Bluetooth API
DiscoverPrompt uses the Web Bluetooth API's requestLEScan() method for passive BLE scanning. This allows detection without requiring device pairing, enabling anonymous monitoring of all nearby Bluetooth signals.
Best Practices
- Scan while moving: The best way to identify trackers is to scan as you move between locations. A device that persists across multiple locations is highly suspicious.
- Regular checks: Scan periodically, especially after being in public places, meeting strangers, or if you feel unsafe.
- Know your devices: The radar will show your own devices (headphones, smartwatch, etc.). Recognize these so you can identify unfamiliar signals.
- Physical inspection: If alerted, physically check common hiding spots: bags, car wheel wells, jacket linings, laptop bags, and anywhere a small device could be concealed.