charles, you know i tested other apps. so here is what i found out today with the seeing eye app. i had my phone a iPhone 4's, fully charged. i started the seeing eye app at a bus stop by my house and went streight up a highway for a 24 minute bus ride. when i got off the bus my battery level was at 85 per cent. now, doing the same with navigon or tomtom / u s a as it is listed on the phone my battery has only went down to 96 or 95 per cent. just wanted to give you that heads up.