wannabe wrote:
SNIP


So how do you feel about an anti-scalding device for tub spicket and
shower!
I was thinking the water gets mixed inside the spigeout, and inside the
shower head.

Anti-scald is part of the shower/tub control (faucet).
It prevents water that is too hot from reaching user.

Another similar device is "pressure balance"
(also built into faucet/control) which maintains
set ratio of Hot/Cold flow even if pressure
drops when someone flushes toilet, for example.

See if Delta site has more explanation:
http://deltacom.deltafaucet.com/wps/portal
Jim