Wake a Windows mobile device via activesync

Is there any way I can wake Windows Mobile device and re-establish a USB
activesync connection to the device from the connected PC?

I have about 100 XP PCs on vehicles, with Windows Mobile 6.1 devices
attached via USB. They run TomTom and provide routing information to the
driver and GPS data back to base.

Occasionally, these devices seem to lose Activesync connectivity. They then
seem to go to sleep (possibly because they are low on battery - because they
have lost connectivity....). Normally, pressing the on button on the device,
or unplugging and re-plugging the USB connection is sufficient to reconnect
and get the battery being charged again.

My problem is that these are remote and mobile vehicles, and as we have
quite a few of them, the number of disconnections grows to be quite high. We
end up chasing round all over the place, trying to reconnect these devices.

I've tried using device manager to disconnect the USB ports, or even
uninstalling the hardware and rebooting. That doesn't seem to work.

Any ideas very gratefully received.

Many thanks in advance

Eric