ARM cortex M0 debugger
The nRF51822 dev kit has a J-Link programmer already on board that you can use for development. Not sure if this can be broken out to program other devices but it might be possible.

Beware of cheap imitations, since they will likely not work with the debug environment due to missing serial number.

More importantly, realize that if you're serious about developing products, you need the right tools. Don't waste time building a hack one and getting it to work unless that's what you want to focus on. Get the right tools and get to work.