[pdimitar]

What feature would win you over for such an app?

For me it would probably be the app proactively reminding me "hey, you marked this person as important but haven't contacted them for a month". Even if this can become a bit annoying it still keeps you in the loop and puts a thought at the back of your head.

<insert it's something meme here>

Another one would probably be the app automatically stalking the person and informing you if they're about to participate in an event where a keyword / tag matches your interests. (That sounds pretty tough to do however.)