Pleasure to have you here!
To answer your questions…
Yes. You can use our web interface to do real time video monitoring.
We have AstroPrint Mobile (on Android) but we don’t have real time video monitoring available YET on the mobile app. But, it’s coming
Based on your connection, there shouldn’t be much of a lag. Even if there’s a lag, your brain shouldn’t notice it – I personally haven’t seen much of a lag with the live streams…
It won’t let you turn off the printer (yet?) – but you can certainly cool down the heated bed. The bed will be nice and cool when the printer is NOT active by default…
Presuming you are talking about the Logitech C920, yes, it is on our list of AstroPrint compatible cameras.
@Neal_Weeks: If you want to test everything out for cheap, you can test this all out with our free, open source AstroBox Gateway (you just need a $35 Raspberry Pi 3).
We also have AstroPrint Desktop – which might be useful for you.
Hope that answers all the questions.
If you have more questions, please start a new thread (since this is all off topic) and I’d be happy to answer them