First of all, grid-tied PV systems that sell power back to the utility and incorporate a battery bank to provide the home's power needs during an outage are quite common. Xantrex and Outback have both offered this type of system for 10 years or more. The SMA product referenced by the OP is a grid tie only inverter, it will not provide back-up power during an outage. However, SMA does make a product called the Sunny Island that will turn their grid-tie inverters into a battery back-up system. This ends up being functionally very similar to a Xantrex or Outback system but at a greater cost.
As for sending power to the Utility; in most places that is called Net Metering. Net Metering has been allowed by law since probably the 1970's. Some utilities and states have different regulations but most use just straight net metering.
The way this works is that any power generated by your solar system is either used by your home or sent backwards thru the meter into the grid. The utility instals a bi-directional meter so they can account for this current flow. In this way you are effectively selling your solar electricity to the utility at the same rate you buy it.
For example, if your home uses 1,000 kWh per month and your solar system generates 800 you would have only purchased 200 form the utility and would only be billed for that amount. If your solar system generated 1,200 that month you would build a 200 kWh credit with the power company. The credit can usually be carried forward for up to 12 months. Net Metering does not allow for the utility to write you a check for excess power generation. To do this you would need a Power Purchase Agreement. PPAs generally have them paying you a wholesale rate for excess power rather than the retail rate you buy it at. Because of this most homeowners don't install a system that will generate more power than they use over the course of a year. This leaves them a utility bill that is essentially zero except for certain taxes and fees you can't get out of.
Buy the way, I instal these systems for a living.
