For two devices to match FHSS hops they would need to have identical chips configured identically. FHSS is the encryption employed by USAF. WHSS isn't officially used anywhere yet. TDSS is hackable with a sufficient data set. TDSS might be broken by a bluetooth sniffer, FHSS and WHSS are outside the realm of reality there...
but you do bring up a reasonable point. 2.4gHz iz a garbage frequency so cluttered with mass produced devices that no one OCD about their security should ever use it. I'd recommend getting a license and using a private bandwidth, or even better, stay wired and use cat-6, or something less common, contained within conduit, the route of the truly paranoid. Don't forget to have all your doors and windows secured with a gauss loop just in case someone tries to actually remove your PC and take a physical image of your storage device. It's way more effort than any reasonable person will go through, but you can do amazing things with a clean room, a freezer, a microscope, and all the time in the world.
Edit: after reading the abstract, not yet accepted by any conference anywhere for presentation, I giggle... These guys think that FHSS devices use a single chip. That's like trying to make a practical claim with a theoretic analysis... actually, that's exactly what it is. They're using a substantially similar process (from what little is described in the abstract) as is used to hack TDSS. FHSS devices work similarly to electronic slot machines. Multiple chips, active chip changes "randomly" as far as computers can conveniently generate, using a TDSS timing chip (or array of chips). I'll amend my assertion to say that it's not impossible under ideal conditions (god knows there's someone out there who's job it is to deal with intercepting real FHSS traffic), but that it is impossible in a practical situation. Also, the abstract makes no differentiation between data encryption and signal encryption. FHSS, WHSS, and TDSS are signal encryption methods, data encryption methods can be used within them, and they can be used within signal multiplexing technolgy (with the notable exceptions of TDSS not working with TDM and WHSS not working with WDM).