TF3D StandBy monitors powerstates like S2U2 does (thx A_C) and turns off or turns on TF3D which allows the device to go into standby.

It’s important to uninstall any previous versions, before installing the new one.

Changes:

– Timeouts are now configurable via register.
[HKEY_LOCAL_MACHINESOFTWARETf3dStandby]
TF3DShutdownTimeout -> Time in MS before suspend, when we shutdown TF3D.
AutoSuspendTimeout -> Time in MS after shutting down TF3D and suspending the device. (This gives TF3D some time to shutdown)
ResumeTimeout -> Timeout in MS to wait before starting TF3D after wakeup.

http://forum.xda-developers.com/showthread.php?t=460621