I love the hackability of Thinkpads circa that generation.

it's incredibly repairable. I still use the t480 for modern workloads because I've been able to switch out the battery, the fan, the keyboard with fairly abundant aftermarket parts.

ThinkPad T480 can be used as a fully featured mobile phone, supporting calls, SMS and mobile data.

Great hack! Is it possible to use a Bluetooth headset?

Of course! You can connect it to any audio source a sink. I had fun with piping music to phone calls with friends.

Nice, thanks!

A setup like this but in phone size would be ideal. The free software mobile world has really been a dumpster fire from the beginning.

Yes, whoever can shrink this down to the size of something that would fit in your pocket would make a killing. Imagine not only being able to make phone calls, but use productivity software and even browse the internet.

A big issue is that the keyboard would take up valuable screen estate.

That modem or a few others can be used with some of the small SBCs, which have a smartphone size or even a smaller size.

If you connect then to some battery pack with a USB charger, you have a mobile solution, though one more cumbersome than a real smartphone.