Ask HN: What would you use a wifi based location tracker for?

I have this prototype wifi based location tracker that works in urban areas whenever there's a wifi connection, will cost $50 (no service fees), and has 1 year battery life with the size of 4AA batteries. It's situated between GPS trackers which charge service fees and Bluetooth trackers which only work within 30ft of you. (i built it for my bike in case it gets stolen... again) What are other use cases? At $9 it could work for 30 days at the size of a walnut