The platform I use, Think or Swim, shows put vs call skews. I would think there are other places on the web where this info is available, but I havent spent any time looking for them. I'm not aware of a search feature for unusual volume for alerts, but keep in mind that volume on options doesnt take into consideration of whether people are buying the calls or selling them (or puts), so I havent put a lot of faith into volume of the options with one exception. If a company puts out positive news and call volume is high, I assume it is buying.
I think investools may have a search feature for unusual volume on options, but I am no longer a subscriber so I cant verify that.