The most interesting aspect of Lenovo's new Moto Z phone is not the device itself, but what it's capable of. Thanks to what are called new Moto Mods, Motorola's flagship Android handset can be augmented with magnetic slip-on attachments that give it a better speaker, a 70-inch projector, and a 22-hour battery pack. Those mods are the ones ready for primetime, when the Moto Z launches in the US this summer as a Verizon-only Droid version. But there are other, more experimental mods in the works.

When the Moto Z becomes available, developers will be able to pick up a reference kit used for designing custom mods. To show off how this works, Lenovo and Motorola brought out two prototype mods at Lenovo Tech World today in San Francisco. One is an LED-lit backplate that responds to sound and a circular display that mirrors whatever is on the smartphone's screen.

These prototypes show how developers can create weird, wacky Moto Mods

The LED one is built directly into the reference mod kit, and you can see exactly how a developer might be able to do some really interesting engineering to make a truly wacky backplate. The display mod is even more nimble, and attaches itself as a square slab into the larger reference mod kit, which is then slipped on the Moto Z. The display mod can be configured to mirror what's on the screen or even let you take selfies with the rear-facing camera by displaying the viewfinder.

These sound like complicated, messy products — and they are. These prototype designs are supposed to be user friendly. But the endless possibilities illustrate how close at hand a truly modular smartphone really is. Google's Project Ara is a bold vision for smartphone that is modular from the ground up. Lenovo and Motorola have a slightly more tempered, and achievable, ambition to make the smartphone modular in steady steps. With the Moto Z, you have the backplate, and that's enough to glimpse the future of Android smartphones.