That is the creme de la creme of disc brake conversions. Actually it will perform better on many suspension setups regardless of whether or not they already have disc tabs. It is however pricey. For a mono-pivot rear suspension, it is almost a necessity for installing disc-brakes unless you want to live with lots of brake-jack. There are other conversion systems which are cheaper for both hardtails as well as full-suspension. Many disc conversion kits are specific to the make and model of the bike. And not all bikes are capable of supporting aftermarket rear disc conversions as they might not have beefy enough chainstays/seatstays/dropouts to take the load.
To the original poster, what exact bike do you have?
Also, you're going to have to consider the front. If your fork is not disc ready then you'll need a fork that is. There are some conversion kits for forks too but unless you're absolutely in love with your particular fork, you might be better off replacing it with a disc-capable one. Then of course you'll need disc hubs for both front and rear (assuming you're converting both ends). And some front hubs require specific fork dropouts which are different than the run-of-the-mill dropouts.
And then on top of all this, you'll need the disc units themselves which include the calipers, lines, rotors and possibly levers.
All of this is going to add up. One solution is to convert only the front as that's going to provide the majority of the effective braking force. If you run discs up front and V-brakes in the rear, you may want to consider mechanical discs as this will allow you to continue using your current levers. This is probably the cheapest solution.
Oh and another thing for the OP... since it seems like you're rather new to this, you may want to enlist the aide of an LBS to perform the work and/or check out your approach.