How to stop all but 1 one app including their services? My HTC Sensation's battery does not last long.
I'm going for a Marathon race which should last at least 5 hours and I'm going to use 1 app (RunKeeper) for that period.  

I would like to preserve as much batter as possible by turning off all other apps including their services e.g. Whatsapp until I'm done with the race.

I've install Task Manager by Toni Dinardo and it seems to have the functionality I need, only not working for me now.  

What should I do?  

Updates:
I've tried another task manager app and it seems that the apps actually work. The problem is services are automatically spawned again after they are killed by the task manager app.
Task killing is never a solution when it comes to "preserving battery". As you discovered, most things restart themselves automatically. What could help, however, is (temporarily) turn off all services you don't need -- after all, it's just for that one run, and (as you already pointed out) you can resign from some of them:


Do you need a data connection for RunKeeper? If not: switch it off, that would save the most. If it's really needed: disable account synchronization, and do the same for all apps which are periodically syncing (e.g. RSS reader and the like).
While running, you won't pickup phone calls anyway -- switch off the radio (if no data are needed: just switch to airplane mode. While in airplane mode, you still can enable some services separately, such as e.g. Bluetooth and GPS). Big savings again
Minor things include Bluetooth. I don't think you want to listen to music via a BT headset while running -- so switch it off. If you really need audio, use a wired headset.
Display: turn brightness down as much as possible. If it's rarely turned on, this might not have much effect -- but it contributes.
Some apps which you won't need "on the run" might offer to exit them completely. Do so.


This altogether should save a lot of juice -- and should preserve enough power for 5h runkeeper with GPS, I'd say. Good luck, and have a successful double-Marathon (one for you running, and one for power-saving ;)!