Wireless bicycle computers come in various shapes and flavors, but here is a very general overview.
The computer consists of a receiver which is mounted on the handlebar. On the wheel there is a magnet attached to the spokes and a sensor/transmitter attached to the fork. The transmitter sends a signal to the receiver every time the magnet passes it.
The receiver, knowing the circumference of the wheel (you tell it this), then counts the number of times the magnet passes the sensor in an elapsed time period and calculates the speed.
Basically, the wireless ones work in much the same way as the wired ones, but transmitting the information instead of sending it through the wire.
My wireless computer also keeps track of my heart rate (through a transmitter on my chest) and my cadence (through a transmitter counting my pedal strokes).
Generally wireless computers are easier to install and look better (no wires threading down your brake cable). Problems can include interference from power lines and interference from other computers. They are much better now, but in early days, if you happened to ride near someone with the same computer brand there was a chance that your speed would double because it would pick up the other guy's transmissions as well. Nowadays most (all?) wireless computers are coded to avoid this problem.
· 1 decade ago