A company called Throwflame is selling one called the "Thermonator" for $9,400. You operate it over WiFi or Bluetooth with a remote control, and it can shoot flames up to 30 feet. (Here's a video.)
The website says they're legal in all 50 states. You just need a special permit in California and Maryland.
They're not pushing the guard dog angle, but they do list eight different things it's perfect for.
They include controlled burns . . . ice and snow removal . . . clearing weeds . . . pyrotechnics or entertainment . . . and also pest removal.
(NY Post)