Wahoo Fitness offers a speed threshold setting to help differentiate between bicycling and walking or other slow motion. So, for example, it can be set to record speeds faster than, say, 5 mph, toward an overall average. That would ignore most walking and slow motion cycling (for example if you're stuck in traffic or behind lots of walkers on the MUP).

I'm not sure whether Cyclemeter offers this feature -- it has so many options it may be buried in a sub-sub-sub-menu.

This could also indirectly provide some privacy buffer. Set the threshold to around 10 mph and it won't begin recording until you're outside and a short distance from your home or apartment (unless you launch from your doorway like it's a downhill race). Strava already has a privacy buffer feature, designed to mask our precise starting/stopping location within a blurred radius of a couple hundred yards or so. I've asked the folks at Cyclemeter to add this option, and they said they'd consider it.

Technically Wahoo Fitness could be left on full time with the motion threshold set high enough to record only bike rides. And perhaps the "stop to record laps" feature could differentiate between rides. But it would drain the battery every day.

A dedicated bike computer would be simpler. Some of 'em cost less than $20. Now that I've used iPhone apps for cycling for more than a year I'm leaning toward getting simple, cheap computers for both bikes.