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.