The nice thing about D*CHAT and D-RATS is that both of them operate in the data portion of the D*STAR standard, and therefore don't involve the patent issues that D*STAR voice runs into. D*CHAT is a basic SMS application for use with D*STAR that has been around for a while now; D-RATS is an expansion on D*CHAT that provides file transfer capabilities, GPS integration, and some simple form processing (which would appear to be really useful in a disaster management context). I'd be interested in knowing if there's an implementation that can be used with any radio, in conjunction with a software implementation of D*STAR. Since neither D*CHAT nor D-RATS use voice, they don't need the AMBE support, and the rest of the standard can theoretically be implemented in software and run out into any1 radio using a RigBlaster or similar technology. In my opinion, this would be a good thing, as it would help to break Icom's lock on the D*STAR standard; a non-Icom implementation of D*STAR (less AMBE) combined with an alternative voice codec, would go a long way to giving amateurs a real option for digital voice that preserves the right to experiment and to innovate.
1As Greg points out in the comments, by "any" I mean "any SSB radio with a wide enough passband". Admittedly, that rules out most of the VHF and UHF radios on the market, since the vast majority of VHF and up radios for hams are FM only.