User feedback collection API service

Question

Tagged with [android] so that someone will actually read this, but applies equally to other application platforms.

We have a number of Android and iPhone applications which have user-feedback functionality incorporated into their user interfaces. These allow the user to leave comments, report bugs, rate the application, request support, etc.

Currently, the applications make a web service call to our backend, which converts them into email and sends them to us.

We would like to replace this with an API call to a remote backend service hosted by someone else, a service that specialises in this sort of thing, and provides us with a web interface for viewing and collating the feedback. The API would need to support arbitrary fields that we can set up as we see fit.

I was hoping to somehow integrate this with the Google Analytics APIs for Android and iPhone, but it's not flexible enough. The likes of FogBugz would seem to do the job, but it's too heavyweight a solution - we don't need anything that fancy.

This question touches on the same issue, but concentrates on self-hosted software. I'm looking for a service provided by someone else.

Free services preferred, for obvious reasons, but commercial options considered also.