I know for a fact that the arduino chip (that I'm using quite heavily these day) has some nice 10bit a/d input pins (6 of them). you can prescale them (voltage divider) and then you'll get 10 bits of res.
there are also some really high bit res chips (24bit a/d) in the $10 range that will output a serial stream, readable easily by the cpu. according to one source, the 24bit chips are a real honest 20bits of analog data (not sampled fast enough for audio but definitely fast enough for a meter!).
that would handle the voltage rails.
for the vu meters, you would want to convert and smooth the varying analog out to some kind of averaged dc - and feed THAT into the a/d pins and sample them as often as you like. getting the 'weight' might be the only tricky part (to keep the meters 'bouncing' in the right way).
I've been thinking of a side project related to this - that would monitor 4 (say) voltage lines and report to the user on some lcd screen. this might be useful on watching bias voltages, etc.
along the same lines, they make temperature reading chips (with i2c output) that you could also read via one of the serial lines and report on.
my background is networking and data-comm and the notion of 'manageable devices' is very key with me
in my world, everything is manageable from airflows on chassis fans, to voltage rails, to power consumed, to error rates, counters, status values and so on. you can literally get hundreds of bits of data when you 'walk' a networking box and ask it for all its manageable entity data.
I almost see the same kind of thing happening to audio, at some point; as controllers get more acceptable to end users and the industry and as people want more and more 'features' on their devices, including remote management.
hmmmm - maybe someday cisco will make hi-fi gear (lol!)
