Automatically enable and disable syncing on WIFI connectivity. Saves money for those without unlimited data plans, out of country, or when simply data roaming. Saves battery by preventing constant 3G/Edge/GPRS syncing. Sync when near an access point by simply turning WIFI on/off as needed.
Sync options are configurable on a connection and disconnection basis. So for example, you can configure it to enable email syncing when not connected to WIFI and to enable syncing of contacts, calendars, and emails when connected to a WIFI access point.
Easy to use, saves battery, and can even save you money in limited situations.
Alerts you if you leave WIFI on and WIFI is not connected. Can be turned off in preferences of by viewing your notifications.