Since then I got the bicycle speed sensor hooked up. There are occassional glitches in the communication with the watch due to power lines and/or large trucks, although this was only a problem once or twice during my cross-country trip. The heart rate measurement is a frequent problem when the weather is dry and the speed or wind is high, possibly due to the wind vibrating the sensors on my chest. Plus the PC software seems to be dividing when it should be multiplying, resulting in the miles being off by a factor of about 2.59 (1.61 kilometers/mile, squared).
The optional altitude sensor may finally be available, but this happened far later than predicted when I bought the monitor.
Here is a new shot of the ride on 5/13/97 (Leavenworth, WA to Coulee City, WA), after manually cleaning up the heart rate glitches (the zero heart rate readings are "real" in the sense that I walked away from the bike):