I see that SGT2005 was curious,

Would this work on a laptop too that uses wifi? 

I would expect it to work ... but ...

IMO, Skype might be the better alternative ... because with Skype, you don't
need (a) a telephone; (b) the MagicJack USB dongle, and (c) an open USB
port for the dongle.  ... OTOH, with Skype, you do need a microphone and
speakers (or headset) ... but many laptops have those built in. 

If all of your 'on the road' calls are to either the office or to your home,
those would be PC to PC calls and are free. 

HTH

--
Martin