One other option to consider is an Aeroforce Interceptor. I got one of these recently and I love it. You can choose what two things you want to display, and have it there on a regular pod gauge for easy reading while you drive. Just don't try to change what is displayed while you drive
It picks up readings from the car's computer and displays them, so there is only one connector to hook up. Ignore the silver switch in the picture, that is left over from the last gauge I had in that spot.
http://www.aeroforcetech.com
