Android only: JuiceDefender, a battery-saving Android app we previously checked out, has seen a major overhaul. Much-needed bug and performance fixing was the big change, but the app also saw a major interface overhaul, and a few new features.
At its core, JuiceDefender is an automation tool that turns your Wi-Fi and cellular data on and off to save battery life. Rather than keep a constant connection option, JuiceDefender turns your data connection every so often—15 minutes, 30 minutes, whatever you'd like — and phones home to see if you have new email, voicemail, what have you. Figuring out exactly what you were setting up before in JuiceDefender made your eyes squint and your forehead furrow, and when you did have a good setup going, there were no guarantees it wouldn't glitch out on you, leaving you without notifications until you discovered it.
JuiceDefender's creator seems to have put in real work at making his app more transparent and useful. The basic app function is to switch on JuiceDefender and let it handle all its power-saving decisions. If you have specific data needs, you can set up specific apps to always have a connection ready when they want them, choose the hours in which JuiceDefender runs, and tweak things like CPU scaling when your phone is idle
The basic, free app in the Market does offer the general on/off battery saving power, but advanced features like location-based Wi-Fi switching and CPU scaling are unlocked by buying the "UltimateJuice" app. That paid app occasionally goes on sale — right now, it's about $5 in the Market. You can grab it from the QR code pasted at left, or search the Market for JuiceDefender.