Nope. The only plugins we use are 1) a MySql plugin and 2) a number converter so we can store Vars accurate to .001 into MySql.

Out client update routine is much like you described. We assign each client a unique id from a master table and we transmit that ID to all clients. Then, whenever a message is sent (by string), this unique ID helps to identify which client the message is for. We use this technique to help us only move the clients we want... so that if Clients b-d are moving close to Client A but not close to Clients e-z, then we send a string with the instructions and unique id's for clients a-d and thus only people near you move.

No plugin needed for this, though a horrible pain to design and test to work.... which is why this is still tops on my list of "things the engine should do" since our system is nothing more than a bunch of lookup tables that we constantly have to reference.