The Gadget: Nyko's Kama, a Wireless Nunchuck for your Wii that syncs up with an included dongle on your Wiimote.
The Price: US$34.99
The Verdict: Works as advertised. We spent hours going through several games, including Mario Galaxy, and the Kama plays just as well as the standard Nunchuck. It's convenient when you're playing Wii Boxing to not have the cable inbetween your two hands, but when you're playing Mario, it's not all that noticeable either way.
The downside to the Kama is having to charge yet another pair of AAs, plus the fact that you're paying a US$15 premium over the standard controller. The upside is you're going entirely wireless, which looks and feels much better. It's also one or two millimeters wider than the standard Nunchuck, which is probably better for adults since the standard one is slightly too thin. Also, the trigger buttons are clear plastic.
Note: We did run into one instance when the Kama kept becoming "stuck" in one direction, always making Mario run off to the left or right. Re-syncing the two controllers didn't help, nor did taking out the batteries and rebooting them. Only shoving in a regular wired Nunchuck or resetting the Wii itself seemed to fix the problem. It probably wasn't a battery issue, since we replaced both batteries with newish ones. We only ran into this once in the entirety of our play time, however, so you shouldn't encounter this often. [Nyko]
Update: Nyko tells me that the issue might be because the unit was from an early production lot. They're sending another one for me to test and see if I can reproduce the problem.