I would like to suggest for the next update of the sprocket app that it would include a countdown to show how many pictures are left to take.
That would be useful, but it would require more than just an update to the App. The Sprocket is designed to be used by multiple devices that could connect and print. The "prints left" feature would require changes to the printer firmware to make assumptions of how many sheets were being loaded (assume a full pack) and to be able to communicate the information back to the App(s) as to how many had been printed and how many remained.
I do remember the "counter" in the old film cameras that would indicate how many were remaining, and the satisfaction of being able to get an extra picture or two at the end of the roll.
It would be nice to have some warning before the paper was running out. I am still on the first set of paper loaded into my Sprocket, I do not know how gracefully the Sprocket will communicate it needs a refill.