I don't believe ove seen anything like that in a while. There used to be something like that, but you also needed to get the same app on the device you were targeting and this app was quickly found a got a lot of couples in trouble
My best suggestion if your stuck on trying to find out what's being said is to get a good sound recorder and place it near where the target spends most of their time. Just a simple tape cassette recorder. Or if your feeling fancy, there are apps to automate it to send to your phone (I believe) and you can save them right there.. something like the paw server would most likely do.