Nyko's Wand is the industry's first Wiimote alternative, and it's a great one at that (see our impressions here). This April, you'll be able to pick it up for $35. Or there are two bundles:
Wand Action Pak
Get the Wand along with the Pistol Grip for $50 this June. The Pistol Grip uses Nyko's proprietary Trans-Port technology to connect the gun's trigger to the Wand electronically rather than mechanically.
Wand Core Pak
Get the Wand along with a Wired Kama (nunchuk) with Rumble for $50 this June.
Buying Nyko's version of the Wiimote and Nunchuk will save you $10, plus pack a few additional features. Having played with the accessories, that makes for a tempting alternative to official Nintendo products...but we'll have to see how things play out when WiiMotion Plus is released.