I’ve been futzing with htop-osx in my spare time to add support for CPU temperature monitoring and fan speed… these are things I like to know when I’m using a laptop, and I figured other folks here might as well. If you use homebrew, just do: brew edit htop-osx and paste in the values from https://gist.github.com/stormerider/5804653 and then brew install htop-osx (or if you already have it installed, brew upgrade htop-osx).
Otherwise, you can clone the fork from https://github.com/stormerider/htop-osx.git and build it manually. Once you’ve done so, run htop and hit F2 to enter setup, navigate over to Available Meters, and add them to whichever column you want (left or right). I normally make htop suid anyways to be able to get full process details, so I’m not sure if that’s required to probe the SMC keys for temperature/fan speed, but it’s possible.
(Most folks will only have one fan; the newer MacBook Pros and the 27″ iMacs only do, I believe the Airs as well. Older MBPs have two, like the loaner I used when getting my MBP repaired. Some Mac Pros– the desktops pre-iMac integration– have up to 4 fans. The code currently only displays 3 of them, the 4th being the PSU fan.)