Unfortunately the Signalink is not a USB Dongle - it is an interface that feeds a soundcard...A SDR dongle is a whole 'nother animal...
TigerTronics Home Page
Such dongles include the Funcube Dongle Pro v2.0, SDRStick and the RTL-SDR with an appropriate up-converter (or one built into the board itself - there are a few like this, some of which are linked in the article below...)
RTL-SDR-the RR Wiki
It certainly is possible - most likely you would need software like Virtual Audio Cable to get the data from the dongle to the PC.
Since you didn't mention which dongle you were looking at, this article by Nils DK8OK is on using the Funcube Dongle on various modes (it's a PDF). There are a couple of errors in the article, but you get the idea that it can be done. There'ss a wide assortment of modes and software that are mentioned here, including using FLDigi on Olivia and MFSK16 (not PSK31, yes, but the concept is the same here)
http://ratzer.at/pdf/Funcube2_DK8OK.pdf
These dongles are also prone to overloading (particularly from AM and FM stations in urban areas) due to rather limited (if it exists at all) filtering (as I've been reading in the various forums and blogs). For a quick portable solution with a laptop (it's even been done with a tablet- see the RTL-SDR Blog) they work, but keep in mind the various limitations with such a setup
Mike