So the word "speeded" was on the front page of the newspaper today. I questioned its validity as a word, but as it turns out, it is a word. "Sped" can also be used.
I think it's a contextual thing, of which sped should be used in almost all situations but speeded would be reasonable, such as replacing "sped up", "he speeded onto the motorway".
I should ask the wife she has a degree in this stuff.