I came across two applications that may be useful:
The extModem application is a command line tool that implements a software packet modem. What's interesting is that it supports the KISS protocol via a TCP port. I have used SoundModem which is very good but only supports the AGW Packet engine API. With extModem and the Virtual Serial Port Emulator I can connect the modem to APRS applications that use KISS modems over COM ports.
The NMEA GPS application is an iPhone application that allows me to send GPS data to other applications over the local network. In this case I can again use the Virtual Serial Port Emulator to connect my iPhone GPS to legacy APRS applications that need to use a COM port.
Below are some notes of how I connected the extModem and NMEA GPS to UI-View32 using the Virtual Serial Ports:
Here is my Virtual Serial Port Emulator configuration