I'm looking to buy a used Prius and I've been wondering, is there any way to check the power level on the main hybrid battery? I don't want to buy a car just for the battery to die within a few weeks.
While that might be good information, I'm pretty sure that the original question was about the HYBRID battery and not the 12 V.
Since the question is now a year old, he probably won't see it anyway.
The answer is: Yes, Toyota dealers are able to test the hybrid battery for obvious problems, assuming that they have the right equipment to do so.
As with many things though, doing that series of tests is not guarantee; the battery might decide to fail an hour later.