Batery back-ups can be DIY but if you don't want to takle that, I bet a plumber would be the 1st call.

A neighbour up the street uses a generator backup, which also provides electricty for other vital home systems. He also keeps a spare pump just in case. (The odd thing is I built and lived in the home next to him and there was never any water problem there. The home he recently moved from is next to my current home that I also built and live in; he had water problems, I don't. Those undergound streams surely are selective.)

Is there 2 sump pumps because 1 sump pump can't handle the load of the water. If this is the case than a battery backup pump may not be able to handle the amount of water that comes into the basement. I would prefer the generator over the battery back-up if the water is too much for one pump to handle. Some great battery back-up systems can be found at www.basementsystems.com
www.americrawlsouth.com
www.basementideas.com
You can also buy them at a local hardware store ie Lowes, Home Depot if you want to diy.