Here's their section on New Hampshire law:
N. H. Rev. Stat. Ann. 570-A:2: It is a felony to intercept, or disclose the contents of, any telecommunication or oral communication without the consent of all parties. However, it is a misdemeanor for a party to a communication, or anyone who has the consent of only one of the parties, to intercept a telecommunication or oral communication.
Civil damages are expressly authorized for unlawful interceptions for the greater of actual damages, $100 a day for each day of violation, or $1,000 in addition to punitive damages, attorney fees and litigation costs. N.H. Rev. Stat. Ann. 570-A:11.
Use of a hidden camera in a private place without the consent "of the persons entitled to privacy therein" is a misdemeanor. N.H. Rev. Stat. Ann. 644:9. A classroom was not a private place where a school custodian could reasonably expect to be safe from video surveillance. State v. McLellan, 744 A.2d 611 (N.H. 1999).