[Russell Sobie]

You can find office chair wheels with brakes on them (I have some, but the brakes on them are pretty poor... but apparently there are good ones out there). You can also build one of these tacky looking things and chock your office chair wheels to something that is attached to your pedals.

Or you can get a Wheelstand Pro and hook one of your wheels in the base, like I do.

Or you can invest in one of these things (I do not have this, and I like still having wheels on my chair, but this does look pretty cool if you are going to have a permanent chair in front of your wheel):