One "interesting" think you can do with GMRS'only' radios (FRS radios are NOT allowed to have removeable antennas), and Hams do all the time
There is a thing called a "pocket J-Pole" antenna - you do have to design them for the frequencies in question, and I have NOT looked for a plan for GMRS (hey, I can go on 2m or 70CM)
The are basically made with a piece of 300 Ohm 'twin lead' television wire - so they roll up quite nicely, and they have a LOT more gain than the "rubber duckie" antennas you typically find on an HT
Go here
http://w4gbu.home.mindspring.com/jpole.htmand use 462.75 as the frequency - of course that doesn't work for 300 ohm foldups
http://blog.mecworks.com/articles/2005/02/27/gmrs-j-pole/