I think it would be a very interesting ability if caffeine could
Have a logged in user have a principle id that functions like a dfx princple giving the user the ability to call query and update calls on active canisters. It could even display the principle so a dev could assign their caffeine principle as an authorized caller on their canisters so functions could be called.
This would be a huge boon to Icp as suddenly mobile/tablet users could interact with their canisters via calls without cli