I found this circuit and use it: It is awesome:
http://hackersbench.com/Projects/1Hz/
I needed a countdown timer for a game -- it needed to count down from 30 seconds -- this works great and it's cheap to build!
I really like the boards from Boundary Devices, especially this one: https://boundarydevices.com/product/nitrogen6x-board-imx6-arm-cortex-a9-sbc/.
All of their boards eat video for lunch! They are great to work with too!