I need to design a device that can transmit an RF signal about 200 meters. The data transferred is very simple. One device simply has a button, that when pressed transmits a two-digit ID to the other unit. There is no other data or voice transmission.
Because the product will be sold globally I'm leaning toward doing 2.4GHz, but I'm concerned about getting the 200 meter range. This range is way outside of most 2.4GHz products. I'm planning on using TI's CC2541 2.4GHz transceiver SoC along with their CC2592 range extender. The CC2592 is supposed to extend the range by up to 7x. BlueGiga sells a Bluetooth Low Energy "Long range" module with a claimed range of 450 meters. So I think reaching 200 meters should be possible.
The other choice is a 868/915/920 MHz system, but that has its own complications, and I would prefer to use a single frequency 2.4 GHz system. Also I'm not sure if 868/915/920 MHz will cover all countries.
So my question is what frequency would you suggest for an international product transmitting a simple ID up to 200 meters?