I've tried things ranging from massage, magnets, braces to wear while sleeping (I tend to fold up my arm and stress the elbow while I sleep, now I can just make sure a pillow is there to prevent that), time off work, using voice recognition software.
My main purchases were a program (to prompt me to take breaks, to stretch while I stop typing and to force me to walk away from the computer at regular intervals), a new mouse, and a small brace for my arm. Mitigating the problem is not cheap, but I want to continue working in software development for as long as possible.
Workpace is the break program I use,
it's available on lots of platforms, comes with a 30 day trial period, and
it lets you customise your rest intervals, break times, and exercises.
Some of the stock exercises bother my elbow, so I removed them via the
On Linux machines, I use the Sytem, Preferences, Keyboard, Typing Break functionality that will lock the screen after a set number of minutes.
On Mac, I found AntiRSI was a good break enforcing program.
Rollermouse has actually come down in price since I bought mine. I credit this for actually letting me continue to work. I test drove about 20 different mice before finding this one that caused zero pain. A coworker can't use it because her hands shake a bit, but my hands are steady enough for perfect control over my mouse pointer with this interface. It connects using a USB port, like a regular mouse, usually no special drivers needed. It has a double click key to reduce clicking and I highly endorse this for anyone who shouldn't be reaching for the mouse. I can't use the button mice built into laptop keyboards, I had to disable the one on my work laptop and only use the touch pad, but for constant use, the touchpad doesn't help me. You can also experiment with the mouse driver settings on your regular mouse (change the speed etc), switch hands, get a mouse platform, get a trackball, use a wacom tablet + pen, basically find what works for you.
One of my diagnoses was epicondylitis, aka tennis elbow. I've found that if I wear a band around my forearm, just below my elbow, it reduces my nerve pain. I wear an Aircast pneumatic arm band at work, and a plainer band at home that doesn't work quite as well. The air bladder keeps pressure on the right spot to reduce my pain and I can't type for long if I'm not wearing it. Ace Tennis Elbow Support is a bit sturdier and doesn't shed foam everywhere.