Hi,
Have you investigated these fonts: Gargi, Lohit Hindi (FOSS) and
Shivaji or Shusha (proprietary).
Keymaps are different to fonts. A keymap is the relationship between
keyboard keys and alphabets. E.g-- in Hindi bolnagri, type p and you
get the hindi letter 'pa'. In Remington, typing p will yield some
other letter.
Type in whatever keymap you want. It's up to you.
Just make sure, before saving the file, select the text and you save
it in the above fonts. If you want to email the doc/odf file, simply
also email the font. When the recipients install that font, they will
be able to read your document.
Hope this helps.