mashtee2003 on "How to find out if a theme is mobile ready?"

Hi,
I just downloaded 3.8.1 and am browsing through the themes,
How can I make sure a theme is mobile ready before start working on it?
Do I need to contact the builder for every single theme and wait for a response? or is there some kind of a library for me to look up the theme's specs and make sure it will work with Handheld devices?
Thanks