I built this CW solid state tesla coil for experimenting with high voltage and fire. It is self tuning to some degree, but unfortunately I couldn't get it to lock on a big enough frequency range for use with chaotic loads like fire. That being said, the arc from this coil is quite fire-like, and is pretty cool on its own.
I ended up building an unusual vacuum tube based design that handled powering burning stuff like a champ, but even then, my power hookup was too limited to do the idea justice. When my new lab is finished being upgraded, I'll re-build the vacuum tube beast and feed it lots of crazy stuff :)