Session Guard is a module to control fishy behaviour of users. Is useful for sites that want to limit the access to the site to one person per user. It detects multiple sessions at the same time and different sessions in a short period of time and from a different location (based on the IP).
It depends on the core Statistics module as it uses the data from the access log table.
Even if you use modules like session limit, that doesn't mean there are different people using your site. Session guard will help you to detect them and take messures.