I'm thinking of using an IR laser and a phototransistor as a basic tripwire alarm using the Teensy 2.0 to do something on my computer after the alarm is tripped. Reading the documentation, it seems trivial to have a Windows event trigger after the voltage on an analog pin drops but I was wondering if anyone has any recommendation as to how I should configure the transistor and any tips towards interfacing with Windows events like screen locking and such. Thanks!