I had a nice Riverwind one, but it broke (not the camera's fault, the cord got ripped out by a truck, long story).
My current camera is a Lorex, a $40 or $50 one from Radio Shack, and it works just fine. Same quality on marestare as the Riverwind was. I'm currently shopping for a Quad processor so I can have mulitple cams at once on marestare, so I need to get more cameras! The cheap Lorex one can be hard to find, not al Radio Shacks stock it.
Unless you don't have a metal barn/roof and NOTHING in between your barn and your house (includes trees), do NOT get wireless.
If you check out the message board on marestare, there are lots of good posts about camera info :)