Clicky (getclicky.com) has a script you can hit to log visits from the backend. Not sure if there is a gem for it, but its as easy as open(url with args) and it records the visit.

Can log custom info, goals, conversions, revenue etc.

I use them for "normal" js site tracking, and now for app tracking without JS and couldn't be happier.

This does do everything in the backend, but it's cloud-based and in their backend. The JS is just the client to fetch and receive the data.