Spell is a standalone spell checker which came out of the Ovation DTP program, and my previous publication of a standalone spell check module. Published in 1991.
It can use the same dictionaries as the Ovation and Ovation Pro programs.
It has a predictive typing feature, at the time a novelty, which everyone hated, pity I didn't do more work to get it right, given the popularity on mobile phones.
Download RISC OS source code