I built this website (www.portacomprimido.com.br or www.pillorganizer.co) in Portuguese and translated to english. It is supposed to check your browser's language and serve the proper language - portuguese for PT-BR, english for all others (doesn't matter which URL you use, both are the same website).
As I not very sure of my coding skills, I wanted to check it, so I asked a friend of mine living in the USA to check it for me. I thought your website would be a easier way to check it, but it is not. All locations show the english version, even the ones supposed to be from "Sâo Paulo, Brazil". If you can correct this, it would be a nice feature.
-Change monitor. If images stop matching, issue an alert.
-More locations in general. Obvious additional server costs.
-Screenshots by user agent; iOS, Android, IE, Firefox, Chrome.
-Screenshots by other variables. Is a particular ISP injecting ads? etc.
Change monitor/alerts would be useful for detecting problems traditional monitor tools may miss. Additionally may be useful in contractual situations where another party is employing cloaking. E.g. I bought a static button banner and the seller is switching it out on me.