In his complaint, John R. Martin alleges that the Nintendo DS infringes on his 2003-filed patent for a "Method for Operating an Electronic Machine Using a Pointing Device," (pictured above) which describes, among other things, a touchscreen input system. Nintendo, for its part, formally responded to the charges (PDF link) by saying it does not infringe on the patents, that Martin's ideas are unpatentable, and that the company is protected by something called the "doctrine of prosecution history estoppel." So there!
We're not patent lawyers, but Martin's patent doesn't seem to offer much improvement over the 1993 touchscreen patents he himself references. Still, he'll have his day in court, and we'll be sure to let you know what happens once that day is done.