You can check in from anywhere you want if you have your phone and an internet connection
I assume you are talking about dropping off your bags, though? For that you will have to go to T2.
There is an airtrain that never seems to be running any more. It's not a very long walk if you don't have too many bags -- if you can comfortably roll your bags I would walk. Maybe a 10 min walk?
I think that the are shuttle buses or something while the airtrain is not running but it's really just easier to walk.