Rails response time and server health monitoring tools -

I have a Rail 3 running in the application production. What are the tools available in the market for feedback time and server health monitoring?

I have information but the response time is only available in the gold version which is $ 200 / month.

Any other device?

I am using serverdency for one year and I am extremely satisfied. Recently a GitHub user has released one for serverdancy.

If you want something else related to Ruby, take a look.