The site offers some good functions, useful to website owners and forum administrators - who's visiting your site, where are they from, that sort of thing.
It's not clear from the site's home page whether they can or do track users' browsing activity once they leave their website -
" Track and search returning visitors and privately monitor people's website browsing activity in real time"
"Use hidden tracker gadgets to conduct a secure surveillance"
If they do that, I would say it's unethical. They can use what tools they wish to see where a user goes on their own site, how long they spend in any area - but once a user leaves the site that's it, they shouldn't follow.
Site is deliberately confusing and misleading for the purpose of corraling visitors and members into purchasing payed subscriptions. Also it seems that free subscriptions run out after a certain period and won't be renewed without payment. If there's a way to renew your free subscription they hide it very well behind requests for payment. I find it all rather deceptive and annoying so I'm done using their services.