Okay .. we all know official keys from BMW cost an arm and a leg and we all know there are alternatives that's much much cheaper.
There are guides out there that teach you how to do this on your own, but nothing that really explain what's what, so here's a quick run down of what's possible and the rough costs of doing so.
Ebay diamond key with remote chipset and EWS transponder - The good ones cost about NZ$45 landed.
To get the keys cut it'll be between NZ$30 - $40 ...
Then it's a matter of getting hold of somebody with an EWS chip reader and transponder programmer that can code the keys to your EWS module (or if you feel like it, buy the tool yourself .. cheapest I've seen are about NZ$80)
Realistic cost of a new working key with remote and ews functions enabled = under $100!!
So here's what to look for:
Remote chipset - I have personally coded both to my own car so I know both work brilliantly and correctly. There are two types out there, both work perfectly fine and will respond to remote unlock and locking coding to the GM5 module: The difference being one has a replaceable battery whilst the other has a rechargeable via the ignition coil (or simply throw it on your Oral B tooth brush charger stand to charge!!).
Left chip set is the rechargeable type - notice the coil - right hand side chipset allows frequency change from 315Mhz to 433Mhz (NZ type!!)
Notice the rechargeable Panasonic Battery on the left chipset
Transponder - there are two types
EML10030A (which is what you will find in the factory keys with remote)
PCF7935 (which is what you will find in the valet keys and earlier larger remote key sets)
Both type of transponders work and will flash with the tools correctly.
My experience shows that the PCF7935 transponders are easier to work with.
Here's what a PCF7935 looks like:
What the key machines do?
Basically you have to open up your EWS box and read the main chipset off it - Each EWS has 10 keys max, that's all. The tools simply codes the ISN password to the transponders allowing it to be recongised and rolling code passed on. You can obviously also lock and unlock keys from any of the 10 sets or write over it with a new transponder. Easy. EWS modules can also be manipulated to provide new VIN number and mileage record.
If anyone needs assistance, I'd be more than happy to help.