I strongly recommend Wii Fit (and especially Wii Fit Plus. Get it for sure.) In addition to the hand sensors you have likely seen, Wii Fit includes a balance board. The Wii board can sense shifts in weight. The way you can try to walk tightropes, get through obstacle courses, ski slalom courses, and bicycle around the Wii island.
There are dozens of games that are very imaginative, and extremely well done. They allow you to work on your balance, your strength, and endurance. Some, like the stepping, running, and biking, allow you to work up a sweat. There are many little challenges to keep you thinking while you exercise.
Speaking as a computer programmer, I am very impressed by the 3-D graphics, the flexibility, and the intelligence built into the programs.
Now: For those who do the free biking, here are the locations of the 20 balloons and the fastest route I've found to get them. I just got off the "bike" and had them in 20:24:25, a new record for me. (I know one place I lost a second.)
If you want to find them yourself, don't read any farther.
To get the balloons in a fast time, start near the top of the mountain, at the balloon on the grass by the stone pillars. That way you head downhill at the start and don't have to climb the mountain again. The free ride starts where you last stopped, so prepare by going up the mountain and stopping after popping that balloon. (Press B to stop there, and exit.)
Also, have you found that the A button rings a bell that attracts a pet? With it alongside you, if you are pointing at a nearby balloon and ring the bell, the dog or cat runs ahead and pops the balloon while you are turning around. Don't ring too soon, though.
OK, here's the fastest route I've found.
1. On the mountain path, by the pillars. Head down...
2. Behind the castle. Keep going around and pick up a pet.
3. Curve around the pond, up on the grass on the right before you get to the tunnel.
4. Cut down slope to tunnel. You will survive and pet will follow. After tunnel, cut right and skirt the cliff to a raised grassy strip. Balloon at end.
5. Go back, up sand path through tunnel with iron bridge. Curve right at exit of bridge. Balloon is in the field.
6. Cut right toward the big rock. Pass it on the right; go across the two suspension bridges, cut up the grass through the tunnel to balloon on sandy plateau.
7. Go back, follow cliff around to left...balloon near the rock.
8. Cut right. This is the trickiest. Coast down and cut sharply around the FIRST fence (passing it with your right shoulder.) Balloon is at far end of a narrow grassy strip. Careful when you turn around.
9. Reverse, follow lower fence; cut around it at end and find balloon near the water by the left side of the bridge.
10. Cross bridge. (You will probably lose your pet.) Cut left at town and take first grass path between houses to balloon.
11. Follow around houses to town square and up the ramp to the upper town. JUST BEFORE you go up, ring bell twice to summon pet.
12. After breaking balloon go back down the SAME ramp. At the bottom, ring bell again. Pet should come running up as you turn right. Head through town, turn down towards water at last street. Go behind last house on right to find balloon (on grass, near water.)
13. Follow black walk, then up to lighthouse. Pass left of lighthouse to balloon on the point.
14. Pick up road that goes around the island. Take immediate right after short tunnel. Balloon is on right side of pond.
15. Another balloon on left side of pond.
16. Cross road, up grass to ruins. Balloon behind ruins.
17. Out of ruins, continue on road through tunnel. Take immediate left down to balloon near water.
18. Follow shore along the sand. (Fastest along the harder, wet sand.) Balloon just past the first large rock with small tunnel in it.
19. Keep going toward end of sand. Go up the jump to the left of the next rock. Balloon on top.
20. Keep going past balloon. Jump down. Keep going. Pick up pet just before final large rock. Follow around the left. Tell pet to break the last balloon.
Now you should have a few minutes to start back to the grass for the long trek back for your next run. (Or try this run in reverse!)