Electronic Arts is the only company selling a Nerf gun that doubles as a Wii remote holder.
Performance Designed Products sent me this N-Strike Switch Shot Ex-3 last week. The Nerf gun comes with three whistler darts and a red viewfinder. You can take the viewfinder off if you'd like and can also remove the air canister and pump that launches the darts.
Then all you have to do is slip the Wii remote into the gun and you've got an over-sized Wii blaster.
The gun doesn't come with it's own game, so I haven't had a chance yet to check out how well it works with Wii shooters. I did test out the Nerf aspects of the gun and managed to ping my son two out of three times.