Note: these haven't been vetted yet
- https://github.com/mattetti/GC-stats-middleware
- https://github.com/bhb/rack-perftools_profiler
- https://github.com/37signals/trashed (requires statsd)
- https://github.com/cheald/scrap (rails metal)
- https://github.com/fauna/bleak_house (requires custom ruby build and/or ruby 1.8.7, not as usable for request cycle)