I'd be very interested to hear about any modifications. From what I can see, the TrackR basically only works within Bluetooth range, but has a "Crowd GPS" function where if somebody with the app walks within range of your TrackR device it will notify you of the location (I'm assuming that you would have to mark it as lost / stolen). The problem that I've read is that the battery life in many instances is only a month, and once the battery is dead, no more tracking. In addition, it seems that the number of people using these is currently too small for the "Crown GPS" functionality to be of any real use.
The other popular Bluetooth tracking device is the Tile, which I just found out also has the "Crown GPS" functionality. You can buy an 8-pack of Tiles on Amazon for $130 (or from the Tile website):
https://www.amazon.com/Tile-Mate-Fin...7HCB8NZEB&th=1
I can't say which is better as I've never used either, but the reviews on Amazon certainly favor the Tile (my guess is mostly due to the much better locating sound that it plays). But, we wouldn't be using the devices for that type of application, so I don't know that it would really make a difference either way. The locating sound that the Tile plays is DEFINITELY better than the TrackR, but the TrackR has a replaceable battery, whereas the Tile does not (they have a "reTile" program that sells you a new unit at a discount). The Tile battery supposedly lasts up to a year. To me, the replaceable battery SEEMS more valuable, but not if I have to replace the batteries every month.
It's certainly not foolproof, nor as good as a dedicated GPS tracker. But, in the end, it MAY better than nothing at all, and the more people that use them and have the app on their phone, the better the "Crowd GPS" tracking. You can buy the TrackR for as little as $12/ea. (they currently have a deal of buy 4 and get 6 free). They also have a waterproof case for the TrackR Bravo (the unit I think everybody on here would want).
Here's a link below to order, if you want. If you order using the link, we'll both get a free one after you order:
https://www.thetrackr.com/?ref_code=C8Op6
Honestly, I'm on the fence (I want to be able to locate my stuff if it's stolen, but I don't know that these would help.)