Rain Sensor for alarm

Wanted to know if anybody knew of any kind of rain sensor that I could use to hook up to my alarm so that when it starts raining it will roll up my windows.  I have a Viper 791XV with both the 530t and 529t window modules.  I've been searching online for a week and can't find anything.  Any help with this would be greatly appreciated.

Thanks

On most, if not all Viper alarm installs, the window modules are connected to the "ground when armed" wire.  In turn, the alarm will roll up the windows every time I arm the car.  But also, I have the door windows set to channel two and the sunroof set to channel 4.  I can roll the windows up or down independently.  If I don't want the windows to roll up when I arm the car, all I have to do is hit the channel two button before I arm the car, that then sends a signal to the roll up modules to not roll up when the car is armed.

And about the rain sensor.  There is a company out there that makes a rain sensor to be used for your wipers.  It will automatically turn on your wipers when it starts to rain and even adjust the speed of the wipers depending on how hard it is raining.   It uses a sensor mounted just behind the rear view mirror and uses infrared beams to detect rain on the windshield.  I'm not sure if I could use that same sensor and hook it up to a relay for the windows because I believe that rain sensor hooks into a controller that has a microprocessor in it.  Plus, that system is $150!  I really don't want to spend that kind of money.  I was hoping someone out there knew of another idea.  I thought about creating my own, but would first like to see if there's already one out there.