If you think you can make money, sure. But "earphones" are dirt cheap. HEADphones are a different matter. Most people today care little about audio quality and look for cheapest price.
Right now I can walk into my local 7-Eleven and buy earphones (ear buds) at the counter.
Putting aside what term you use, do you really want to build up a whole business selling head/ear phones when you can get them everywhere dirt cheap, including Ebay ?
By develop did you have in mind a store that sells the product, or a site that might have reference information and/or reviews, and that links to where they are sold (and make money off say Amazon affiliate revenue or Adsense)
I would probably work out a rough business plan trying to estimate revenue and see if it is worth the hours that it would take.
I presume you have knowledge/expertise in the area, so it might not be much work to set up a mini (few page) site, see how much traffic and revenue it gets, hopefully pick up some backlinks, and that might help you get more for the name even if you do decide to sell it at that point.
ps BTW GoValue estimate the worth of your name at over $18000! The .net of the same name sold for $1200, so that would seem to suggest that the name is worth mid $$$$ in .com. The .ca also sold for over $1200, and usually .com at least a factor of 4 over .ca of same word (not always obviously but for most generics).