I used one that had a 'dimmer' function on each switch. It controlled four 50 watt, 120vac, halogen lamps.

It worked OK but the lamps did not come up to full intensity, maybe 95% of maximum. It bothered me enough to pull wires.

...

I have used wireless switches for many years to do exactly what you want to do. Very few stores cary them - your best bet is buying on line.

I have used both X-10 and Insteon brands - my new house is loaded with Insteon switches. You can buy them at www.smarthome.com.

For your application, look at the 3-way dimmer kit which comes with two switches that are pre-programmed to work together. They make both decora paddle type and push button switches.

You will need a hot & netutral wire at each switch location for these switches to work. The switches communicate wirelessly as well as over the neutral wire to provide a dual network. To work with maximum reliability, the neutrals connected to both switches should connected to the same breaker (best) or at least on the same phase - this allows the over wire signals to pass between the two switches. If you can't get an over wire path via neutral wires directly, the switches will still work through the wireless path but depending on the seperation - you might get some intermitant results.

I second the reccomendation for the Insteon switches. They are available as on-off or dimmer type and can be set up in an n-way configuration. Some Home Depots sell them or order from SmartHome.com.

In most houses, all neutrals are tied together at the neutral buss in the distribution panel.

Think you very much for the feedback. I may not have explained myself well enough. I now have a light controled by a 2-way switch. I want to make it a 3-way system by adding a second switch in a location where it is not practical to get a wire to.

what you mean is that you want to add a 4way then. A "2way" switch is actually called a 3way. If you have a light controlled by two switches they are called 3ways, if you want to add another switch thus making it so the light is controlled by three switches total, what you need to add is a 4way.
I personally don't know of a wireless 4way switch but I'm sure there is something out there.