The 27/49 MHz RC cars and such uses a special purpose chipset designed just for remote control toys. It's not necessarily easy or even possible to use them for general purpose data communications. You should be able to find some more information on some of the RC forums; there was a lot of interest in converting/enhancing these for custom modeling applications. (if you can figure out the right keywords. Try "bitcharger conversion" : Micro Thread Index (the best place to start) - RC Groups )
Also, radio has weird legal issue attached. Just because a given band is 'license free' for use by remote control toys doesn't mean that you are ALLOWED to use that band for other purposes (like data transmission.)
And the $100 radios you're talking about have much larger capabilities than the 27MHz remote control radios. You might get a couple hundred bits/second out of a cheap remote control (10 values/s times 3 channels time 8 bits, or so?) in one direction only, compared to the ~10Mbps receive and transmit capabilities possible for an 802.11 wireless networking board.
Richard mentioned the JeeNodes that are essentially arduinos with lower-capability radio at prices similar to an arduino...