I'll agree with this as well. There's a massive amount of reference designs available, from ARM Cortex M embedded designs to, and in no particular order, ADC's,

I'll agree with this as well. There's a massive amount of reference designs available, from ARM Cortex M embedded designs to, and in no particular order, ADC's, motor controllers, power supplies, touch sensors and so on from vendors like Freescale, NXP, Texas Instruments and so on and on. A15's plus hybrids like Exynos's and Omap5's are fairly closed, but for most of the real time functional apparatuses many want to play with, if excluding Ethernet and GPU's, these aren't the most suitable anyway. For serious hobbyists there are some interesting off the shelf SoC's. The main challenges are about production.