As of quite awhile back you're not able to meet people at the gate of the arriving flight.
However, I've come across certain sites like Churchill Executive Cars, which offers a concierge service that supposedly allows an agent of the company to meet the client at the gate or even on the tarmac and help them through the Immigration and Customs this one specifically in JFK but they offer similar service in other major New York Area airports.
Additionally, we have tarmac service available that would allow a passenger to de-board the plane directly onto the tarmac where their luggage will be loaded into a private car, taken to a private immigration area, and then dropped with a Churchill Executive Cars driver outside the terminal to take them to their final destination.
On arrivals, we will have a Churchill Executive Cars Agent meet the passengers at the gate when they de-board the airplane. The agent will have a sign with the passenger's name and Churchill logo and have a baggage porter ready to carry their carry-on bags. The agent will then whisk them through fast-track immigration and customs, and pass the passengers along to the Churchill Executive Cars driver to be taken to their final destination.
Now if this is true there is a way for someone to have clearance to go airside to meet a person but I was unable to find any references on how such a clearance can be attained.
So is this real? And can this be done by an Average Joe?