It is definately one way. I believe they have 8 MB of flash ram. Here's a link.

http://www.pronto.philips.com/pro_spec.htm

I had actually thought about a small touchscreen lcd tied into the serial port. I didn't even know if that were possible.

Made for Home Theater but applicable for everything. Here's a link to a btrmaps for DSS.

http://www.prontoedit.com/html/bitmaps.html