Is there anyway to check if your phone is in your pocket?

I want to have Tasker turn on vibration if it is in my pocket, and turn it off if it isn't. That way at work it won't vibrate when it is on my desk, but it will in my pocket.

I tried using the proximity sensor or light sensor, but Tasker says that those don't run when the screen is turned off, and I want it so if I take it out of my pocket and put it on my desk, without turning the screen on all, for it to turn vibrate off.

Does anyone know a good way to do this?