One potential option is using one of the JRuby 1.7.x releases, which still supports the Ruby 1.8 language level. You'll be able to use all the JVM tools, such as VisualVM, which offer similar functionality.

I think support for Ruby 1.8.7 has ended, so it is very unlikely you will see anything like this written for that version of Ruby. You should seriously consider migrating from that version.

Having said that - As one of the authors of Rbkit - it does not even work on 1.9.x - because instrumentation support we require from Ruby isn't simply there.