Bike riding is excellent for bums, legs, calfs and even tummy's so I would imagine stationary bikes would be the same. If you can make it harder then easyier with resistance then that will tone even more muscles. Changing the position of your feet can help work out different muscles as well. Try pushing with the tip part of your foot then the heel part to work out a greater range of leg and bum muscles. It's basically all round great non weight baring exersize. You do miss out on upper body but that's about all.
Logged back in 2012. CW 128 GW 122
cw 161 Goal weight 140 as of june 2005