Bell invented the photophone, a device that transmitted speech on a beam of light. Although not commercially successful, it was a precursor to fiber-optic communication.

Bell developed an induction balance metal detector in an attempt to locate a bullet lodged in President James A. Garfield's body after an assassination attempt.

Bell became fascinated with aviation and experimented extensively with kites, particularly the tetrahedral kite, a design based on tetrahedral cells. He believed that kites could eventually be developed into heavier-than-air flying machines.

Bell founded the Aerial Experiment Association (AEA) with Glenn Curtiss, Thomas Selfridge, and other aviation pioneers. The AEA produced several innovative aircraft, including the Silver Dart, the first powered aircraft to fly in Canada.

In his later years, Bell became interested in hydrofoils. He and his associates designed and built a series of hydrofoil boats, culminating in the HD-4, which set a world speed record for watercraft in 1919.