First try unplugging the battery. Leave it sit for a bit 30 mins then re-connect. This may do it...basically you need to reset the ECU. Otherwise do what Homer does. Put a piece of black electrical tape over the blinking light.
Well if your handspring accepts modules in the back, you could get the OBD 2 Module for it but it isn't cheap. Somewhere around $400 or so. My brother has it, but I think it only works on 98 and up models, any car by the way. He let's me use it sometime and I love it. You can drive around and it shows you all the live data on the fly. Sort of like the Skyline GTR that has such toy build in as stock. Freakkin' PS2 cars... hehehe
If you looking for some software for your PDA just search the web for Mr Taxi. There you should find tons.