'Tune up' is the iTunes tag fixer. It's legit software, but feels like a franken-monster hybrid to me (it attaches itself to iTunes windows in a weird way).
'Tune up' is also used a lot as a strap line in 'Mac Keeper' aka 'Mac Cleaner' adverts that pop up everywhere. It is supposedly legit, but it feels malicious due to their use of invasive advertising. It seems they market it by setting up many sites with 'reviews' with nice disclosures featuring …
This website abides by word of mouth marketing standards.
They are basically trying to get page rank in search engines whilst they are bombarding Mac software sites with their adverts.
It popped up around the time of the 'Mac Defender' fake security trojan (which is malicious). So they both seem dirty to me :)
It's a shame OnyX won't get into the App Store, it could do with the credibility of being vetted by Apple.