According to Facebook, it is impossible for a person or an application to monitor who is visiting a profile. Facebook simply does not allow it. Moreover, Facebook requests that users report any app that claims to be able to do this.
More often than not, these applications are packed with malware that spreads across Facebook profiles and into users' computers, making them vulnerable to identity theft and other crimes. While it is likely that Facebook itself keeps track of which users have viewed which profiles, the company does not disclose this information to its users. For business pages, Facebook Insights provides useful information, such as the number of people who interact with the page and how many people like it, among other useful statistics for businesses.