In reply to Howard J:
Not used them personally and an interesting ruggedised design but I'd note they're ISM frequency band not UHF like standard walkie talkies. That gives them more bandwidth (and regulatory freedom) for digital modulation and coding stuff (though I'd assume they're using off the shelf wireless IOT hardware rather than anything too custom).
However it'll also make them inherently shorter range, they claim "up to 600m" but that'll be seriously compromised when not line-of-sight. They make a thing about "ad hoc mesh networking" which is retransmitting around a group to extend the effective range, but that obviously won't help if it's just you and a partner!