I've been a slacker on the pushups but I've been keeping on with Wii Fit, mainly with the aerobic workouts. I enjoy the Basic Run Island Lap. It doesn't use the Wii Balance Board but it does use the Wii remote: just hold it or stick it in your pocket and it registers your steps like a pedometer.
The metric they use to measure your progress on this exercise is "burn rate," which as far as I can tell is a measure of how consistent the run is. If I'm just screwing around and shaking the remote up and down while I'm running and making my Mii fall, my burn rate will be in the 10-20% range. If I give it a good try and do a reasonable job, the burn rate will be higher: 80% to 100%, or more. When I'm running in place on the floor, I can get a burn rate anywhere from 150% to 250%. I don't know how they calculate it but it's probably inversely related to the variance in the step rate: the more the running speed changes, the lower the burn rate. There's also a speed component: a slower speed seems to give a higher burn rate than a faster speed, even if that faster speed is steady.
I forgot to take a picture of my 403% burn rate Island Lap, but here's how I did it. This might be cheating but my calves, ankles, and lower back tell me otherwise. I bounced for 15 minutes on a trampoline we got at a yard sale. Nice and steady! And probably lower impact than running, anyway.