i was looking into buy a pioneer DEH-P77DH and it has this feature. DFS alarm + it says its an alarm but doesnt say how it works or what features it has. anyone know?

I have this feature on my Pioneer DEH-P720. You can add an inputs for door triggers, shock sensors or hood pins. There is also outputs for sirens or horn honk. Can arm and dissarm by removing and installing the faceplate or using doorlock triggers. Can be interfaced with a seprate alarm. Once triggered the DFS alarm outputs a highpitched sounds through your stereo and is VERY unconfortable. I use mine with my alarm to take car of the inside sirens.

Over all it is a good thing to have to use with a seprate alarm but can be a pain used on its own. 30 secs armed after removal of the face and 30 secs to put the face back on before alarm activates. NOTE times can be changed from 5,15,30 secs.

do you ahve msn maybe you can tell me a bit mroe about it ? cause imn preety interested

As stated the alarm on it's own (w/o added accesories like pin switches or sirens) will arm after a user selected time (5,15,30s) when you pull the faceplate. It will go off after entering the car in the time selected unless you put the faceplate back on otherwise it sends a screaming tone through your stereo speakers.
It's a good idea but really will only get used once in a while otherwise it is too easy to forget and a pain in the a**. Think about opening the passenger door on a date with that girl who finally said she'd go out with you and forgetting to get the faceplate on in time. Understand?
I didn't bother to hook mine up in this car. Just get a good alarm.