I have successfully run Echolink in sysop mode using a Rigblaster NoMic (which I normally use with my HF rig for PSK). You will need to configure the Rigblaster for your particular HT. Here is a link to the microphone connection setup:http://www.westmountainradio.com/supportno.htm
Of course, you could build your own equivalent circuit if you wish.
You will need a serial port on your computer for controlling transmit keying. If you have a newer computer without a serial port, you can use a USB to serial converter (available cheap on E-Bay). The Rigblaster has the built in serial port circuit for keying. Or you can build one yourself - as I recall it just takes a few diodes and resistors.
Hope this helps.