DIY Wireless System Recommendations?

[yp@xxxxxx]

I want to install a wireless alarm system in my house.  I've been
visiting some websites that sell them.  Can anyone recommend one that
has all or some of these features:

1) Uses N-RAM so if all power is lost, even back up battery, the
system will retain its settings and not require setup again?  Will
be fully operational/configured when power restored.

2) Can use your computer directly(not going through a website) to
setup/download/upload system settings?

3) Components such as Motion Sensors are reliable but not real
expensive?

4) Easily programmable, user friendly.

I am thinking of having 3 magnetic door switches and about 5 motion
sensors.

Also is there any precautions or special needs when using magnetic
door alarm switches on steel doors?  I know the steel can rob some
magnetism but what if they're installed with spacers so they're
mounted about 1/2" away from door?

Any information appreciated............