you don't really need an app - just turn down the brightness, turn off wifi, 3g, Bluetooth when not needed.... close apps that run constantly in the background waiting for push notifications, such as facebook.
Originally Posted by old bill2: “I Need to try and extend the battey life of My HTC One as much as posible. Can anyone recomend be it free or chargable some power saving apps to try ?”
The best battery saving app is Snapdragon battery guru from Qualcomm. It is free. Of course you need the right processor, but you have that in the H1. The app monitors your use for three days then it shuts off the stuff you don't need. It is really really good. Give it a try.
I've found Llama to be a bit unreliable. I use Setting Profiles to do things like trigger a work profile with no wifi or gps when I'm at work. Can be based on locations, calendar events, times etc.