sounds like the keyless entry antenna went out, or the brain box dealing with them. they have a bad habit of doing this. I've had almost my entire keyless entry system replaced including the request buttons themselves.
There are many reports of failure for the Mazdaspeed6 GT keyless entry/ignition system. Most people report that one of the buttons stops working (usually the trunk). If that is the case with yours, just take it to the dealer and they will fix it for you.
If you have a standard keyless entry system where you need to press the button on the keyfob to unlock the doors then that is a different issue...of which I haven't seen any reports. In any case, take it to the dealer if it is still under warranty.
And if that doesnt work, try to find a good car audio place. Most of them install alarms and keyless entry and are pretty handy with the stuff for a lot cheaper than going to the dealer. If you find a decent one with good people they will probably be your new best friend when it comes to that stuff.