Some great ideas, guys - thanks! I was initially thinking about this by making/buying a edge guide for my plunge router with a point, or a bearing to ride along the scalloped (that's the right word!) edge. I saw that Bosch makes a roller bearing guide for the trim router. I've also seen what appear to be guides for Dremmels for banding applications. But, I think I'd rather use my larger plunge router for this job. It also seems like it might be a bit hard to control using this method. Anyone have any experience with these types of edge guides?
That aside - I think you guys are right - a template and a bearing bit or bushing is the way to go. My template in the photo is a quarter of the final board, but I think I'll make a full size template and then try Bill's method by also making a smaller template so I have a controllable slot for the bushing to ride in.
Thanks again for the ideas!