hey dude... bharat_r... it's not that easy to get a thermal image!!!
Just by adding fancy RBGs to the picture, u don't get a thermal image... go to the basics... the warmer parts of the pic have to be redder & the colder parts bluish...
Not as simple as NIGHT VISION... dude...
The plugin u showed does work wonders.. but this tutorial is just to bring in another concept into Photoshop idealogy....
Btw... ur gradient map method was good.. though not realistic!!! It's against the laws of physics... for god's sake!!!