...isn't new or original but has proven itself many times.
I continuously run both my PC's and a laptop off two inverters which are powered by four deep cycle, lead-acid batteries and a good charger. It isn't the most elegant solution...you wouldn't want to do it if there wasn't sufficient space and ventilation, for example. But it does the job nicely and has the added plus of being a good surge suppressor. It is fairly expensive to set up (batteries, charger, inverters) However, it gives me about two hours of reserve power and has worked well in the past.
Should my frame relay line and ISP go down, the plan is to bring up my trading software on my "email" machine (the laptop); it takes less than thirty seconds. I have it using a dial up to connect to my backup ISP (Earthlink) and is always on and connected during trading.
I suppose that something may come along for which I have no contingency plan but, so far, all of problems that I've encountered can be handled by my backups.
Hope this helps...