Do you have an iphone that was not jail broken? you would probably know if you did.
launch Safari and type Cydia://
If it launches and App called Cydia your phone is jailbroke...
Click on Manage...
then packages....
then look through the list for Smartphone or Core Utilities (lib)
If either on on your iphone then someone has installed one of the more popular monitoring software packages. and are reading every text and email and aware of every call you make and receive as well as can identify your location at anytime via GPS
if you cannot get into Cydia......
Go to your dialer and dial
*12345 or
**54321 and push call..... watch closely.... Did the phone "spring" (clear the screen then display the apple icon and then come back to the dialer or home page?)
If so.... You have been hacked,,,,,
Android phone...... Do you have Android Toolkit listed as an installed app?
In the dialer try dialing *12345# and press send....
Does it bring up a login page? If so you have been hacked....
There are other software packages but this one seems to be the one getting the most attention....