Just keep in mind - Installing a keylogger on someone else's computer(a computer that does not belong to you (- a child's computer is a different story) is illegal. Your own computer is fine, installing it on a smartphone or a computer that belongs to another person is NOT. It violates federal law. I would get in touch with a lawyer asap before doing anything if you fear something will happen within your marriage. The last thing you need is a broken or stretched law to effect the outcome.