There are many companies they make aftermarket BMW Scan tools, some are doing just basic functions like readand erase fault codes, some have more featured functions like actuations and some basic service functions, and some BMW Scan tools they come with some adavnced features for professional technicians.
Before you decide what BMW Scan tool you plan to have, you must sorting the requirements of your job, this will help you to be more prices of what BMW scan tool you need.
The two channels of CANBUS act like a gateway the simulation of which helps to join both DME and CAS fast and connect them to WVCI. This enables us to several important functions like ISN reading, programming of keys, DME and CAS programming etc at ease. When it comes to key programming issues in the BMW E and F series. This further leads us to better reading, writing, blocking, saving or deleting keys from the CAS.
If you watch above video, the technician was using Autohex II BMW Scan tool to read BMW DME ISN from old unit, then he used the this ISN to write it to the donor DME, this video was informative. for more information you can check this BMW Scan tool