Traditional ways of giving flesh to your suspicions is through hiring a private investigator that will give you information based on observations after tailing your subject.
The problem with this method is that it hurts on the pocket – think charging every hour – not to mention that observations alone does not give you results you want.
Try a mobile phone spyware download that gives you professional results minus the rip off! You can use it to monitor multiple units and it is undetectable. It only takes a minute to set up and after that you have unlimited access to the mobile phone all you want.