This is it: Nitro. It comes with source code so you can take a look at all the stuff I recently wrote about. I will also put the hacked TSerialEndpoint and the TSerialChip implementation on the web at some time.
Nitro for now advertises it's services under the "ircm" label. Any application that wants to make an IrCOMM connection should use this as the service identifier. For applications that haven't been modified (e.g. the NIE Modem and Serial support module), patching the application package by replacing the Unicode string "aser" or "irda" with "ircm" should do the trick (Unicode strings use two-byte characters, in this case the high byte is zero and the low byte is the ASCII code). I've provided a patched NIE Modem & Serial module on Nitro's web page. I'll try LookOut as soon as I receive my USB IrDA dongle.
Eric Schneck (of iTunes Plug-in fame) has had success using Nitro with his Motorola Timeport T280, Earthlink and SimpleMail. I have currently some trouble for establishing a PPP connection with a Nokia 3650 with Radiolinja as the provider, so this calls for some logging capabilities to find out what exactly happens.
Other missing pieces are a working OBEX layer (which shouldn't be to difficult), the associated data handlers and a way to not only initiate but also accept incoming connections.