I saw their product on Dragons' Den yesterday. I found it rather surprising as I've bought similar bluetooth key fobs, from Aliexpress for around $1.40 each and they mentioned they where planning on selling them for around £20.
One that is very successful (4.5 million sold) is https://thetrackr.com. I have no affiliation--I just hear their ads over and over on lots of podcasts. They sell them for about $30 each, so they are similarly more expensive than AliExpress type ones.