OpenSignalMaps, which is an app that gauges local cell phone signal strength, recently studied its users to see just how much fragmentation there was when it comes to the number of device models.  The results are thus:

The number of different companies to make the devices is almost as large.

The different resolutions on the various devices is also staggering.

And finally API levels show the varied versions of Android that people are using.

Source: opensignalmaps.com