I looked into this extensively in December 2013 so that I could remotely monitor my ski cabin. I couldn't find any good solutions for simple notification of the door status. The choices were:
* Opener add-on, like the Chamberlain MyQ. (No service fee. I chose this excellent solution.)
* Webcam with motion-detector that can email you a notification. (Not a perfect solution.)
* Home-automation-gateway with door status hardware. (Most require service fee.)
* Home-security system with door status hardware. (Most require service fee.)
I use
Chamberlain's MyQ WiFi universal garage door opener (~$130 at Home Depot, or $
110 at Amazon) with their free MyQ app. It's very easy to install. No wiring required. For legal reasons, they want you to install it on the ceiling over the garage door (so that people can see & hear the pre-close warning light & beeper) but it will work as long as you plug it into an electrical outlet just about anywhere reasonably near the garage It works with practically any brand of garage door (wirelessly like a universal remote) and it connects by WiFi to your home's router. It lets you remotely open and close up to 2 garage doors and check on their status. (For a second door you have to buy a 2nd sensor for ~$30.) You can optionally have it send emails/texts* or push an alert to the MyQ app for different types of door activity (such as opened, closed, remained open for X-minutes). It works really well. Pricey, but I love it.
* Actually, the MyQ server won't text you but you can have it email you, and then set up your email system (like in Gmail's, or Hotmail's web settings) to automatically forward any emails from Chamberlain to your cellular provider's free email-to-text system. That's what I do because I didn't want the MyQ app's push-notification service to always run. Email-to-text works very well. (See following link.)
Use Email to Send Text Messages (SMS) to Mobile Phones for Free