FWIW I found the G Shock article timely: http://www.macrumors.com/2012/12/05/...k-smart-watch/
When paired with an iPhone, the Casio smart watch can automatically set its own time, alert you to incoming calls and email, and locate your iPhone from the watch.
I would think that something like this might actually be a fair alternative to your idea. A low power wearable BT device that tells you when you are being separated from your phone and helps you locate it.
Find your phone is great, but the few times I've used it to notice that my phone is home, but I still don't know WHERE at home.
MBA (13" 1.7 GHz 128GB), UMBP (15" SD 2.8 GHz), UMB (13" 2.4 GHz), iMac (17" Yonah), 32GB iPad 3 WiFi+LTE, 64 GB iPad WiFi, 32 GB iPhone 5, Airport Extreme