Some work better than others depending on your business type and how much traffic you get. The one I've been using for about six months does what it says and hasn't had any major issues. Captures emails when people log into the WiFi and lets me send campaigns from the dashboard. Reading feedback through a link like this helped me avoid ones with bad support or technical problems. Pricing varies but most are in the 30 to 60 dollar range monthly. The cheaper ones sometimes have limits on how many customers you can capture. Main thing is picking one that matches your visitor volume and has decent reviews from actual users not just marketing hype

Questions like face ratio often come from curiosity but focusing on health and confidence is more important.