My brother had one to sort out one of his girls at work.........
She failed to come back from lunch, and as this was unlike her he contacted her to see if she was alright, and found she she was in tears.
It turns out her husband who was supposedly at home all day was in fact in a hotel in Cambridge. She had suspected something was going on and also looked up her friend on another app (Google latitude), and voila a certain convergence of their locations was discovered
She had phoned the husband of the friend in question, they proceeded to the hotel and found both cars in the car park. They then swapped phones so she was telling his wife that she was in the lobby, and he was telling her husband.
Two messy divorces!
