WiSync
A free, completely transparent, WIFI synchronization assistant for your Android phone. Save Battery. Save Money. Save Time! Even better, WiSync doubles as a Locale plugin. If you're a Locale user, WiSync is a must have application.

Automatically enable and disable synchronization based on your WIFI connection status. WiSync can save money for those without unlimited data plans, out of the country, or when simply data roaming. WiSync does not interfere with independent synchronization efforts and can be easily disabled.

WiSync can save significant battery life by preventing constant background synchronization over 3G/Edge/GPRS connections. In stead of constant synchronization, synchronization is disabled until you connect with a WIFI device. Once connected, WiSync automatically synchronizes the providers you configure. Simply turn WIFI on and off as needed to control synchronization or allow WiSync to automatically do its thing by leaving your WIFI turned on. Leaving your WIFI constantly enabled will reduce some of the battery benefits.

WiSync activates based on a WIFI connection and disconnection and otherwise does not run in the background; ignoring normal Android service lifecycles. Users can independently configure which accounts (email, calendar, or contacts) are enabled and disabled on WIFI connection and disconnection.

WiSync is easy to use. In fact,WiSync transparently works for you and never against you. It does not interfere with independent synchronization control. Best of all, its free and supported! And contrary to commonly held belief, WiSync compliments applications such as Locale and Power Manager, saving your battery power in ways these applications simply can not.

Want to see what people are saying about WiSync? Learn how WiSync can significantly extend your battery life at AndDev's Forums; which has additional links and quotes from ModMyGPhone.

DISCLAIMER: WiSync does not prevent the phone from constantly collecting and reporting statistics back to Google. WiSync does not directly prevent data roaming charges. WiSync can help reduce or completely prevent roaming fees incurred when synchronizing your phone by preventing synchronization until free WIFI access is available.