Installing with Rails 3
Getting Flying Sphinx set up on Rails 3 is pretty painless - there's just two steps. Firstly, let Heroku know (if you haven't already) that you'd like to use the Flying Sphinx add-on with your app:
heroku addons:add flying_sphinx:wooden
Wooden Sphinx is the entry-level plan, and unless you've got a large amount of data to index, you're probably going to be fine on this. However, feel free to peruse the other plans on Heroku's site.
Next, you'll want to add Flying Sphinx - and Thinking Sphinx, if you're not using it already - to your Gemfile. Thinking Sphinx 2.0.4 or better is needed, so, it'll probably look something like the following:
gem 'thinking-sphinx', '2.0.4' gem 'flying-sphinx', '0.7.0'
Bundle, deploy, and away you go!