I cannot tell you the number of times I've needed to use a synth or pop a glimmer buff while in battle. I'd have no problem finding a quiet corner for a second and loading the menu, but the UI sometimes takes so long to load that it's counter-productive to my fireteam to bother.
If I could activate those items from the app, the same way I can do a quick armor or weapon swap, it would be extremely helpful.
I don't know if you can turn in bounties from the app, but considering you can now do it from the menu it would be convenient, if not all that necessary.
I don't however think we should be able to purchase things from vendors through the app. Especially from Xur. Unless we're at some point working openly with The Nine.
Yas bangie plsz mak ths ideas 2 b hapening iam need primery bullits b4 menu can b lodeing it is's big pane n my pooper 2 b died by nite bcause no bullits,