A drunken driving test may not seem the likeliest place to come up with a mobile phone app, but that’s when inspiration struck Nashville resident Clay Bradley. He told The Nashville Ledger that he was following a policeman’s pen with his eyes when he thought a smartphone could be used for the same purpose. He mentioned his idea to a couple of friends, and they came up with BreathalEyes. The 99-cent app launched in November and can be used to measure involuntary eye movements when people are intoxicated, which is one method police use in field sobriety tests.