Q Entertainment announced in Famitsu this week that they will be releasing Guardian Hearts Online on the Playstation Vita this month. Similar to how they released Angel Love Online on the PC and later on the Playstation 3, Guardian Hearts Online will be a Free-to-Play release that is powered by optional microtransactions and is based on an original mobile release by the company a couple of years back.
Unfortunately there seems to only be a slim chance of this being released internationally unless you have a Japanese Playstation Network account.