I made https://CampAlert.live , a notification service for last minute camp site cancellations. It sends you an email and text message when we find a free spot of your choosing. Currently, it supports only Canadian campsites in BC, AB and National Parks.

I've looked into previous tools but their services were all too expensive. They also didn't have the granularity I wanted in the options you could choose for campsites. We tried expanding to the USA last year but since we made it a paid service, it's been hard to advertise and get into the market. When we were free for the first month, we got multiple local radio interviews and news stories which really helped bring that critical mass of users in.