I am going to sound sneaky and awful but I was desperate to find out if exp was cheating on me but he had two phones, a blackberry and and iPhone.
He would never leave them near me until he worked out how to password the bb then he quite happily left it laying around knowing I couldn't do anything with it.
So I waited a few weeks until he was over confident and whilst my phone was on silent I sent him a jokey text (he was sitting next to me) and secretly filmed him putting the iPhone code in. It was always to fast for me to see properly but I could watch it back over and over and found out what the code was. But I couldn't get hold of the phone for a while so decided to just sit on the info.
With the blackberry, I left him a note one morning saying I'd had an email from tmobile saying there was a problem with the account and he needed to email them the following information. I included a reference number that he would have to send and asked for his phone number, pin and password. I wrote down the email address that I had created especially (I used mail . com as I could include the word tmobile in the address) he emailed the information and I picked up the email and then had the password!
I had both passwords but no phones! I saw the iPhone in the footwell of the car - he always left it in the car, and waited until he was asleep and sneaked outside and stole it. I turned it off and hid it under the bed until he was at work. From that I found he had been on dating and casual sex sites, had lots of profiles and messages, photos that looked to real to have been downloaded from a porn site. I could also read his emails on it. I turned the phone off and left it hidden, he was so cross with himself for losing it.
Waited until he had drunk to much and was crashed out in bed and took the blackberry from his bedside table, took it downstairs and put it on charge hoping he would think that was where he had left it. Read his texts and found the evidence I needed.
He is now exp, I know what I did was sneaky and underhand but I felt I was going crazy. I also felt I needed a valid reason to end the relationship for some reason.