There is a app called voxer that is available on smart phones. It allows instant half duplex conversation on smart phones. It makes the smart phone like a walkie talkie. It is a lot of fun, but it is problematic for hobbyist and providers alike.
The biggest problem is that it uses the numbers in your phone to give you a list of voxer users to communicate. Which would be fine if it was like a phonebook and and only showed you who you could communicate with, but it also puts you in the other person's list. So if you have a providers phone number is you phone book, even if you have never actually contacted her yet, she will see you in her voxer list.
That alone isn't that bad because it will not give the other person your actual phone number. And it would only tell the other person that you have their number programmed. What makes it a possible problem is that if your real name is in the setup then they now have your name.
This also bypasses the security of using google voice if you have the numbers programed in your phone for providers, but use google voice as your hobby phone.
Most important is if you use it do not use it on a phone that you also use connect to facebook. Or rather don't use the connect with facebook option. This will show the person who only had your phone number before, your facebook account. Photo and name on your facebook account is all it shows, but it all it takes is a search of facebook with the information and you can be found.
If you are wondering I have tried it by randomly adding phone numbers from BP and ECCIE and a have the face book accounts of a few providers. They of course see my information at the same time though.
A fake name on voxer would be the easy answer, but then all my family and friends with voxer would wonder who diud-diud was. No way to actually connect it with me as anyone with their number would show up in their voxer.