Grid synchronizer

Why do you want to synchronize ? If you are on the generator, you are reducing the amount of power you draw from the grid. An auto transfer breaker to switch back and forth between sources will be cheaper.

If you want to synchronize so that the generators excess power flows into the grid (and you get paid for it), you had better call your utility and check with them. The interconnection requirements vary between utilities, and the rules for a emergency or standby generator interconnection are often different than the requirements for an alternative energy installation.

Your electric utilities service provider will need to know if you are going to synchronize a generator with theirs and connect your generator with their grid. This is a must. You could facing big legal issue's if you don't. The nations power grid falls under the jurisdiction of national security.
http://www.basler.com/html/rscrel.htm

I am going to assume that you do not have the generator as yet.
Go to the Alt-E Store and look at the Xantrex SW5548 inverter. Read the specifacations. You will see that it is built with relays that allow the user to chose either grid (or genset) or battery power just by flipping a breaker off or on. The user would have to size a battery bank as well.
An example-
Choose certain 120 vac circuits such as lighting and general receptacles. Move those circuits to a separate smaller breaker panel. Determine the total watts ( the SW5548 is good upto 5500 watts continuous) and the watt hours they would consume in a 24 hour period. Feed the inverter from the main or sub panel. Grid power will pass through under normal circumstances to the dedicated circuits and maintain a charge on the battery bank. In a black out or if you turn the breaker off that supplies grid power to the inverter, the inverter will power those circuits from battery power. Then as time and or money allow, add PV modules or wind genny's or micro hydro or whatever to charge the batteries instead of grid power. The cost difference between this system and the one you speak of will be relatively the same when you consider the fuel and maintainace required on the genset over over a lifetime. Off grid living is most cost effective for those who want live so far from the grid that it would be less expensive to buy all of the RE equipment than to buy a line extension. Or you could do it just to be able to brag to your friends that you dont have an electric bill every month;}  

Synchronizing your generator to the grid can be accomplished by several products available out there. Beckwith, Sweitzer(SEL), Encorp among others can be used. However, Synchronizing is just part of the procedure. You will have to apply with the utility for parallel operation of your generator with the grid. The utilities will require you to submit an application which would include short circuit analysis, electrical plans and protective relaying schemes. This is costly and you may have to contact engineering companies to do this for you. If you are still interested you can look at our website at www.palsonsengineering.com.