I have a cell phone that if I left/lost it somewhere it'd still be there when I got back, no worries someone would want to keep it if it was as they would be running after me to give it back. I thought for sure I was going to have to finally replace it this year as it seemed to have sprung some sort of leak that left a big black spot on the screen...which is basically about a 2x3" square that I've never figured out how to operate the internet on, thank goodness as I would never stop blogging if I did, then as mysteriously as the spot appeared it started to disappear, now it just a tiny dot at the top of the screen, now I can read text again and no longer have to consider pictures I take "a shot in the dark" so to speak.
After watching people obsess about losing their phones for years, particularly if I happen to be giving them a ride to and from said lost destination, whereas the words I fear most is "omg I just left my phone (insert location)", and can be particularly distressing to hear during rush hour traffic, I would gladly not only support but buy each and every person a device that loudly proclaims, "hey asshole don't leave me here" when they have reach a distance of about twenty feet from their phones.
Haha yeah the device has something like that which would let you know if you were leaving home without something you need which is useful!