Back in 2011 in early year 2 of University I designed a module phone. I had planned how the network provided a certain number of upgrades/ modules through the year to keep the phone fresh (as we all like new things!). Only way to describe it is a big fat aluminum pebble, it wasn’t a looker but the concept was there. You opened it up and the modules fit inside. Slightly embarrassing to look at now but hey, it was a start. Then came the Google Ara a few years later (well to the public anyway, probably had the idea in the 90s or something). I think it’s been canned anyway 
I will try and post a picture as I recently binned old work from my behance.