Nice article. It might also bear to mention that not only is 900mhz frequency hopping more secure. Typically 900mhz has a longer range. For example our standard transmitters have a typical range of 1200 ft open air and our High Power Receiver tests out at 1.7 miles.
Also the two-way nature of (at least the DMP) 900mhz wireless offers some advantages. Single message & single ack, reduces battery drain. The ability to adjust the detector over the air, sensitivity, pulse count, put it in walk test or even put it to sleep in the disarmed state all offer unique advantages. The ability to push a message to the wireless allows for wireless relays, sounder, lights, and even wireless smokes that sync their sounder. (commercial fire UL864 listed).
There is more. But I'll give you all a break. :-)