TextMate

To make TextMate leverage chruby, point TM_RUBY to a shim.

Shim with auto-switching

#!/bin/sh
source /usr/local/share/chruby/chruby.sh
source /usr/local/share/chruby/auto.sh

exec ruby "$@"

Shim without auto-switching

#!/bin/sh
source /usr/local/share/chruby/chruby.sh
chruby ruby

exec ruby "$@"

Note: Make sure the shim is executable by running chmod +x /path/to/shim.