This system just recognizes motion by reflected ir waves on the subject, and for the laser, any cheap laser pointer would do, example: http://www.ebay.com/itm/Mini-LED-Flash-light-Torch-Keychain-Laser-Pen-PURPL-/190732252540?pt=US_Laser_Pointers&hash=item2c6887357c
You just need a laser pointer and a photoresistor hooked up to an Analog Input and +5v, where you can set the threshold for the ambient light in your program. If you need any help for the program I can help you. But your best bet remains the reed switches, if it's not a big deal to put screws on your door frame...
http://www.ebay.com/itm/White-Door-Window-Contacts-Magnetic-Reed-Switch-Sensor-/350611210023?pt=LH_DefaultDomain_0&hash=item51a20e7f27