Have any of you tried one of these?

It's a small device you place on or in something and then you use an app on your phone to tack it.

https://www.amazon.com/phone-Halo-TrackR-Sticker-Smartphones/dp/B00KJLMLFW

I don't know the range but it sounds like a device that might have a lot of uses. I just wondered if anybody has used them and how good they work.