Don't get too excited, though. The cost ($15.98 per flight for the first 2K and 10 cents per K after that) is going to be rediculous.
JetConnect Email is an extension of the already-present JetConnect service, which redirects modem calls made on the Verizon AirPhone to the JetConnect server on the plane. This allows for caching and aggregation on the plane and faster communication between users on the same flight. The basic service costs $5.99 per flight and offers IM, Text Messaging (one way), stock quotes, weather, etc.