This Kindle eBook was written in 2003 and self-published in 2010 on Kindle:
http://www.amazon.com/America-The-Enslaved-Neurochip-ebook/d...
In the future 2032 the US government passes an N-Chip law putting neurochips in the brains of the mentally ill and people with a criminal history in trying to control them. The two main characters got tricked into making the chip and this megacorp modified it. It has backdoors to shock the brain unconscious or to death. People rebel and protest, and are killed by security guards and police with neurorifles that activate the backdoor in the chip.
Free for Prime members, otherwise 99 cents. A good sci fi story but needs work on grammar and other stuff.