Ladies and gentlemen, mostly gentlemen ,
I present you my last project (i hope i dont get arrested 
)
http://www.youtube.com/watch?v=Rx8gKg_CGfA
For educational perposes only!
I am not responsible for any damaged houses , cars or terrorist attacks !
Hope you like it!
Oh while am at it, i need some help!
All the arduino does here is read an LDR and turn on a relay (cellphone's vibrating motor is replaced by an LED)
I want to remove the arduino so that anyone can make it. To do that i need a circuit that can turn ona relay based on the state of the LDR.all i can find is "when the laser is pointing at the ldr is stays off , then the beam gets broken the circuit is turning the realy on"I want the opposite , so I need to change that schematic :
That is an N type MOSFET, can it be done if I use a aP type (to make the LED glow when the laser is shining on the LDR)
If not how can i do that?
you don`t need a FET, an ordinary NPN transistor will work and probably cost less, a BC108 or 2N2222A2N2222A etc...
turning On or Off with the LDR is simply a matter of Where you put it to bias the transistors base.
so leaving your circuit as it is, and moving the LDR and 2k2 resistor around will turn the LED On with light and off with dark, just swap them over 
Do you mean like this
i wasnt shure thats going to work, but makes sense
that is what I meant, yes 
the purpose being that without it you have nearly a direct path via the E/B junction between + and - should the LDR resistor value drop too low, this risks damaging the transistor and/or the LDR.
with a resistor in line you can still measure the PD, but at safer current levels.
