Just a quick heads-up to 3GS users with old-bootrom and running 6.1.3 as they may probably run into the same problem: My iPhone has shown the typical signs of something's using the CPU all the time, draining the battery very fast and making the phone both warm and sluggish. The great tool Top I've previously recommended previously too in several threads here has shown the following: As you can see, it was locationd that has continuously used the 100%. I've quickly found out that it wasn't any location service or automatic time update service (all disable-able from Settings disabled them all for test) that forced it to continuously use the CPU. Neither did any jailbreak tweak (tested this by just running Cydia, which disables most JB tweaks). After a while, I've found out it was iCloud. After a disable in Settings (with deleting local synchronized stuff) and re-enable it with all the features (including Where's my Phone), the problem was gone. During all this time, continuously watching the results returned by top was of great help. I could immediately see the effects of dis/enabling a certain, location-specific feature of iOS, third-party apps or JB tweaks. Without this, it would probably have taken days to find out it was iCloud that caused the problems.