Clock system

It's a clock challange open to make the ultimate clock that I joined (please go there and vote). Since it been a while I feel it's time to write down something about what I'm up to in regards to it.
I looked around a lot trying to figure out some new way to present the time but it's not that easy. I was thinking on things like a bookshelf, Domino 9, gear clock, rolling ball, Propeller clock and many many more but whatever I thought about it was already done a thousand times.
I talked to a friend for ideas and he suggested to attack the backend instead. The plan is to make a clock that is modularized. It has a base with the smarts in it. Then you plug in a presentation module on top to show the time. In the base you have holes/slots where you can plug in modules for atomic clock, GPS time, ntp over wifi (both receiving and broadcasting), your smartphone, radio, audio and so on.
The units communicate over i2c/spi bus with some defined protocol so that you can plug in things and it just discovers it and starts using it.
Now the first version will be some 3D printed base with modules that plug together. For display it can be a simple 7SEG display or analog clock that is just put on top.