A couple of CESes ago, Monoprice launched a couple of 22-inch pen displays to compete with the Wacom Cintiq 22HD. Shortly afterward, the products disappeared from their website and line-up, so I assumed, at the time, that they changed their mind or otherwise refocused.
Turns out, it was only temporary. There are now two models on their product list, one for $499.99 and another for $599.99, although I have a feeling that the cheaper model might be discontinued. The only real, concrete difference that I can see is the $599.99 model uses “battery-free” pens, which I'm assuming is powered by induction from the display surface. The cheaper model is out-of-stock with an estimated availability of “TBD”. That one uses rechargeable pens. The $599.99 model also lists Linux drivers. The $599.99 version also has a slower response time (12ms vs 5ms) and higher viewing angles, although both are listed as IPS.
Whether or not the $499.99 model will become available again, the $599.99 one is still about a third of the price of the Wacom Cintiq 22HD. Also, unlike the Wacom, it supports Linux as mentioned above. They used to offer a pen display with a ten-finger capacitive touchscreen, which competes with the Wacom Cintiq 22HD Touch, but that has not been relaunched, at least not yet.