The BMW EWS is happy to read the info from either the circuit board on rechargeable keys, or the PCF7935 which is the RFID chip, and is totally self contained.
The wallet key for example has one of the PCF chips inside.
ID44 is part of the identification in the chip, the BMW ones will come pre-prepared with 44 as part of the ID string. Different cars use different IDs, and some car chip writers can take totally blank chips and set the ID code, but the majority need that bit pre-programmed.
They can be programmed by a few different bits of kit, the most common is EWS editor lite, another one is what I've got, and that's called the AK90, and they are pretty basic, and are limited to the pre "smart key" keys.
Next step up to do the smart keys tends to move you into a £300-400 range, and the blank keys are pretty expensive meaning you might as well go to BMW for a new one.