Looks like they're running on 900MHz. To be effective, 900MHz antennas usually must be rather large. May limit the useful applications.
Edit: I stand corrected. http://www.slashgear.com/whistlegps-dog-tracker-first-to-use...
Edit: I stand corrected. http://www.slashgear.com/whistlegps-dog-tracker-first-to-use...
Coming from communications engineering I find ultra band modulation scheme intriguing. I haven't seen any papers that on what this is exactly and am waiting for more information to come out!
Ps: there is work on metamaterial based antenna design to shrink antenna dimensions http://en.m.wikipedia.org/wiki/Metamaterial_antenna