I've just read about very interesting product - 0patch. Occasionaly, we got to know that some companies didn't fixed the bug which is causing serious vulnerability. When it becomes public sometimes we have to wait months for an official patch and 0patch want to provide own unofficial fixes.
The idea is simple: they prepare small patches which are applied by 0patch agent in the runtime. That solution uses technique called function hooking to modify existing code. They also shared manual for developers which shows how to prepare own patches.