Like Gujarati, Modi is a variant of Devanagari that was developed in about 1600 AD. Like Gujarati, it was used mostly for accounting, then later for administration.
It looks very similar to Devanagari, but with fewer ligatures, rounder/”swoopier” glyphs that are faster to write (and harder to read). Like Gujarati, Modi got rid of Devanagari’s inconsistent headline, but unlike Gujarati, Modi always has a headline instead of never. If you look at examples of old texts in Modi, it looks almost like the writer drew the headline before or after the rest of the text.
Links: Wikipedia, Omniglot, Ancient Scripts, Unicode proposal