I don't think it necessarily means a lady has a pimp. A lot of ladies use a safety system of letting someone they trust know when they're with a client. A lot of horror stories out there prove that when things are going right, they can take a turn for the worst and go left out of nowhere. A young lady just was found dead in Sacramento on Tuesday (Alert thread). Her friend posted a thread on another forum asking for help because she got a call from her pleading for help. The call ended abruptly with sounds of violence, but the young lady had no idea where to even send the police. Se had no information. All she knew was that her friend went to Sacramento to work.
I have my own safety measures in place. They don't consist of calling in front of the gent, but you can guarantee that someone always knows where I am, what I'm doing, and how long I'll be busy. Once, I had a gentlemen extend our arrangement on the spot. I forgot to inform my safety, and she freaked out blowing up my phone when she hadn't heard from me when she was supposed to. It was an honest mistake that made me realize just how important that safety net is not only to me, but to those who may be waiting to hear from me as well. I'll never put her through that again.
Edited to say: I also know a lady who only calls her safety once her client arrives. She says she does so just to make sure the gentleman doesn't get any funny ideas. She DOES NOT have a pimp. Not sure if that's the case here, but it could be.