Air locker is good but expensive, between $1200/$1600 fitted (from memory) cos they come with a compresor.Lockrite or ezy locker would the same benefits as an air locker (in my opinion)
at less than half the price.If you want to know about either units, ARB sell the ezy locker and 4wd systems(SA) sell the lockrite,the latter having a fair bit of info about how they work on there web site.My brother in law has lockrites front and rear in his Hilux and recons they are golden for off road, but you will have to work out if they're rite for you.