Backstory: I recently moved to Austin, TX from Baltimore, MD with a cat. Not the most enjoyable ride but we made it safe. The most frustrating part came when I booked a hotel late at night and there wasn't any pet friendly availability. Not all open hotel rooms are pet friendly.
The Idea: Pet friendly hotel search.
Deep Dive: Very similar to existing hotel searches but you would target pet owners. This is a two sided marketplace, once you get a few hotels on board and target some seo keywords, your end customers should show up rather quickly! None of the big players have this feature.
Validation: I spent 30 minutes in Virginia calling hotels to find an open room.
Monetization: You could sell very targeted, pet focused, advertisements on your site.
Steps to Launch: I would target one hotel chain in one specific city and add all other hotel chains but have they grayed out. Once you have some traction with one hotel, it will be easy to get the others on board with the initial proof. All the other ones will be suffering from fomo!