There are plans to improve the Sortd mobile app.  However, we've prioritized development of an official Gmail add-on (which runs inside the Gmail mobile app itself).  You can get it here.  Once you've installed it you'll see Sortd icon at the bottom, which will bring up a Sortd menu.


Just a note that it's very new and Google have had some problems with add-ons on iOS, which they hope to resolve soon.