Hi Chad,
MyDoorOpener will work over Wifi and 3G/LTE. In order for it to work properly over 3G/LTE (internet),
you'll typically have to configure your home router to have it forward external/internet HTTP requests
to your Arduino controller's internal IP address. Typically this is done using what's called
NAT port forwarding.
Also, since your ISP most probably changes your external/internet IP address once in a while, you'll
probably also want to look into some sort of
Dynamic DNS system to make sure you're always up-to-date
with your home router's latest IP address.
It's quite easy to do, but if you're not familiar with these concepts, you'll have to look up how it's done
for your particular home router as it's somewhat a little bit different from router to router. But it should be
very easy and it does remain accessible even for the non technical. If you Google around, you'll most probably
find blog posts that explain how it's done for your particular home router.
Hope this answers your question.
Best regards,