You download an app - and your phone will be logging when you come into contact with another person who has a similar, or the same app thanks to Bluetooth technology.
Nowadays everybody and their brother has a smartphone pretty much attached to their hand so its no question that accidents happen, but what happens if you drop your phone in the toilet?
How many times have you ever had to make that all important phone call to your grand kids in New Hartford or your husband in Clinton only to realize your cell phone was dead?!