My iOS app has an email button in it and I do get feature requests and bug reports from time to time, I also have a subreddit for the small community, when I was more engaged in marketing I was posting more there and getting some responses but I've lost a little motivation lately.
It's definitely worked well in that regard, better than other things I've tried in the past and I think it helps communicate that I'm just a single person building an app in my spare time rather than a big company.
