It isn't meaningful for a WiFi-only iPad or an iPod, for example. But it's only useful for cellular products. Contact Mac Tools Customer Service to learn more about becoming a franchisee, get info on warranties, and other information.
That said, Apple can use the IMEI to identify the phone, as there is a one-to-one relationship between IMEI and serial number, and their systems do use it.
And in general your cellular carrier doesn't know the serial number of your device unless you bought it from them, and even then they don't really care about it. If your office or home phone works via SIP, you can use that phone number on your Mac anywhere you have decent Internet connection. It can be used to call regular phones via any appropriate SIP provider. However, it is essential for your cellular carrier to manage your phone. Telephone is a VoIP program which allows you to make phone calls over the internet. So it isn't useful as a universal identifier for all Apple products. I would like to understand why a phone has both an IMEI number and also a Serial number please It also has a WiFi MAC address, a Bluetooth MAC address. The serial number fits Apple's universal serial number system from the serial number alone Apple knows what type of device it is (iPhone, iPad, iPod, Macbook, iMac, etc), when it was made, and it uses it to track the warranty status. You can talk to an Apple Advisor by calling the Apple Support phone number for your country or region. It also has a WiFi MAC address, a Bluetooth MAC address, an ICCID, an MEID, an SEID and probably a couple I have missed. Your phone has a lot more than IMEI and serial number. I would like to understand why a phone has both an IMEI number and also a Serial number please? what is the purpose of having two unique numbers for a phone?