I just need some general guidance as to where I should go with this one. I want to use the photon to update firmware on another microcontroller. I am using an SD card that hooks up to the Photon so that it has more memory. Basically, instead of having to plug in my microcontroller(say an arduino for example), I want to be able to wirelessly reprogram it by using the Photon. So I would reprogram the photon wirelessly, and the photon would reprogram the microcontroller that it is wired to. Is this practical? Is the photon a good device for doing this? Any chance I can get some guidance as to how I should do this? maybe this topic is covered somewhere else.
@SlinkyMation, why not just use a Photon in the first place and skip the other processor! 
Not sure if you’re joking or not, but I work for a company where we already have this processer with tons of crazy firmware written to it so yeah. I’d rather not.
Could you elaborate how you are programming the other device?
There is a similar project where a Photon is used in place of a SWD programmer to unbrick another Photon
Disclaimer: This is a prove of concept and not for production use
@SlinkyMation, yup, I was just poking. Like @ScruffR said, it all depends on the target. I believe the code that he pointed to has actually been tested to revive a “dead” Electron or Photon via SWD. 