Aaron-

>Anyone know if an ASP.NET client can monitor a standard serial COM port in real time? For example, there is a device connected to the serial port and while a particular ASP.NET page is loaded in Internet Explorer it will have to monitor the serial port communications and act on it.

Dick Grier is an MS MVP and is the serial comm god. He's updated his classic book on the subject to include .NET, so it might be of some help to you:

http://www.amazon.com/exec/obidos/ASIN/1890422274/ref=ase_hardsoftwaacompu/002-6364810-3666435