As Steven says, FireWire capture from a DV source is just data transfer – no processing and no access to elements of the stream like there was with analogue.
On the other hand, if your source is analogue and you are using a bridge to generate a FireWire input, then a readout of audio levels during capture could be very useful since you will be able to adjust audio levels in the analogue domain before its conversion to FireWire.
If you need to watch audio levels during capture, then Scenalyzer Live has this facility. http://www.scenalyzer.com has a trial download which watermarks footage but is otherwise functional before you buy.