Telephone Hold Button Kit K-18: Once this K-18 Telephone Hold Button Kit is assembled you may put all incoming and outgoing calls on hold at the press of a button!
ELENCO K-35 Telephone Bug is only the size of a quarter, yet transmits both sides of a telephone conversation to any FM radio.
VELLEMAN TELEPHONE AMPLIFIER KIT K4900
Velleman Remote Control By Telephone Kit K6501
Velleman Remote Control VIA GSM Mobile Phone Kit MK160