How does it work

It chucks in more fuel to spool the turbo quicker iirc

How much will it cost

Dependant on spec, need a turbo with ALS and also the ECu has to be able to control ALS

What are the dangers

Shortened Turbo and engine life.

Is it a DIY fit option or who will fit this for me

Yes can be DIY, theres a guy putting an antilag T3 into his FWD ax !
But you still need to take it somewhere to get it mapped up correctly