How can I identify the current terminal emulator from a bash script?

I'm not sure how to tell iTerm and iTerm2 apart, but check the $TERM_PROGRAM envar. For me (Mac OS X 10.7), it returns Apple_Terminal for Terminal.app, and iTerm.app for iTerm2.

Working fine on Ubuntu & mint Linux--

ps -o comm= -p "$(($(ps -o ppid= -p "$(($(ps -o sid= -p "$$")))")))"