Induction heating has been around for a while and is used extensively to melt metal in foundries. The advantage is the rapid heat up and the ability to achieve temperatures above molten state.
Induction heating works by using a high frequency alternating current, so that the atoms trying to continually realign themselves with the changing magnetic poles generate heat.
For melting metal, a ceramic crucible with a coil of copper allow tubing, through which cooling water flows, as well as the high frequency current, is used. The water prevents the coils from overheating and melting themselves.
On smaller units, solid coils are used, but typically are limited as to duty cycle. In our application the coil needs to be robust enough for us to heat up a nail, without overheating the coil.
I've mentioned high frequency current, and there needs to be a supply, and wall plugs aren't always handy, so I was particularly impressed by the nice battery operated design that Hard Boiled Frog came up with based on a Sky Ray King aluminum flashlight.
Kudos and accolades to Hard Boiled Frog, whom shares that design here: