Rev Robotics also makes a servo called the Smart Robot Servo. Here are the features of it from their website.
The REV Robotics Smart Robot Servo (SRS) is configurable metal-geared servo that takes the guesswork out of aligning and adjusting servo based mechanisms. One SRS can be used as a standard angular servo, a custom angular servo, and a continuous rotation servo by simply changing its settings.
Default Operation
Out of the box, the SRS operates like a standard 180° servo, responding to a 500μs – 2500μs RC servo pulse.
Smart Features
Unlocking the smart features is simple with the REV SRS Programmer (REV-31-1108 – sold separately).
Angular Mode
With the press of a button, the SRS Programmer can set custom angular limits without removing the SRS from the mechanism. These custom limits eliminate the need to fiddle with servo horns or linkages.
Continuous Rotation Mode
With the flip of a switch on the SRS Programmer, the SRS can switch from angular mode to continuous rotation mode. The SRS saves time and money by preventing the permanent modification of standard servos.
http://www.revrobotics.com/product/smart-robot-servo/