Pennsylvania has adopted the Uniform Interstate Deposition and Discovery Act, which act was originally drafted by the National Conference of Commissioners on uniform state laws.
The point of this legislation is to minimize the process for out-of-state counsel who want to conduct discovery in Pennsylvania.
The new law provides that a litigant from another state would have to submit a subpoena to the Pennsylvania Prothonotary in the jurisdiction in which the subject of the subpoena resides, works, or regular transact business in person. Once the subpoena is served, the subject of the subpoena retains the right to apply to court for Orders to modify or quash the subpoena issued by the out-of-state litigant.
Googling this topic also reveals that the same act is possibly under consideration in New Jersey as well.
Obviously, the adoption of the Uniform Interstate Deposition and Discovery Act in both Pennsylvania and New Jersey would help to streamline and make discovery efforts more efficient and cost-effective on both sides of the Delaware River.