To note, I'm not interested in simply 'hiding' content for mobile devices, I want to filter out that content completely. I'm also not trying to address the issue by building a mobile specific interface (mob.example.com).
There was another question regarding something similar:
The solution, in that post, was to set a session during the initial request, and then use the session to filter content on subsequent requests.
I primarily develop in Rails, and I'm wondering if there are any gems or ruby-specific solutions to this problem?