If you have a Propeller Activity Board WX and your computer has either the Windows or Mac operating system, you can program your propeller over Wi-Fi. This is an especially useful feature for the ActivityBot [1] and mobile robots, and other projects that are not convenient to keep tethered.
Links
[1] http://learn.parallax.com/tutorials/activitybot
[2] http://learn.parallax.com/tutorials/language/propeller-c/propeller-c-set-simpleide