I never found the website that was providing this kind of service or feature. Im only seeing people are doing it manually and it doesn't even need a lot of time to do that. Opening any explorer will take only 30 -1 minutes and expecting you wanna do that for 5 blockchains and you will be wasting only 5 minutes. I think that this is more than enough to give you a temporary answer for your question while you are waiting for someone to create such website. I were also looking for this website in the past but i have made my own private site to monitor the gas fees in any blockchain (getting limited into the popular chain only that i often used it)