TB15,
A few thoughts:
Most wifi cameras transmit to a phone/tablet, etc. so the HDMI hookup is the hard part.
Does your TV also have a composite input? If so, there are lots of radio transmitting cameras (not necessarily wifi) that have a receiver that has a composite video output.
If it has to be HDMI, you can get a composite-to-HDMI converter for under $25 (amazon).
If you can live without "live" video, you can also get lots of small, inexpensive video cameras that take a microSD card, and will record a much better (in most cases ) video that radio transmitting cameras... why?... our layouts have lots of noise generating circuits in the area. Recorded video will be a perfect picture (with sound), but will not be live!
Just a few cents' worth!