Mobiprox 1.0

the author of this app says:

ProxSync is a utility that provides automated synchronization over Bluetooth for Windows Mobile devices. ProxSync will run quietly in the background whilst the device is in sleep mode and check occasionally for the proximity of the selected Bluetooth synchronization partner. If the partner is found, the device will be brought out of sleep mode to connect over Bluetooth and perform a synchronization. Once the sync is complete, the connection will be terminated and the device will return to the sleep mode.

The user interface allows for control of the frequency and times of the day and week that the device will check for its sync partner.

Never miss appointments again because you forgot to sync.