It’s pretty damn simple HYIP Monitor is an overview and analytical website, which monitors the current state of HYIPs, and displays the current status of investment funds. As a rule, there are four status of HYIP programs: paying, waiting, problem, not paying.
HYIP monitors also display the basic parameters of HYIP programs: investment plans, the max/min deposit amount, affiliate reward, types of payments (instant, automatic, manual), payment systems HYIPs work with, HYIP start time, and brief description of the project.
There are must-read articles for a better understanding of how HYIP monitors work: