This sounds more like a servo motor situation than a stepper. Servos get a pulse value sent to them that determines its final position. With a stepper, you have to synch both the controller and stepper to a zero position and try to keep them in synch with an encoder.
But a typical servo has an inherent zero position. You send it a 1.5mS pulse and it goes to its zero position. You keep sending it this pulse every 20mS and it "locks in" to that position. Send a narrower pulse, down to 1 mS, and it starts to turn to a position from zero. Send a wider pulse up to 2 mS and it goes the other way. Either way, it has internal stops you have to respect. Modified servos can be made to turn continuously one way or the other, 360 degrees. You need to determine what strength in ounces the servo needs to arrive at the servo's ability to hold the device it is attached to in place.
Once again, I recommend this all-in-one motor controller from BasicMicro(.com), the $25 Nano Driver Board:
**broken link removed**
The simple USB programmer is just another $15. Once you finish programming, you can use this device to do serial communications with a PC or other serial device. This is a total controller solution for $40.
The best feature of this driver board is its ability to work with so many motor types. It can do servos, simple DC motors, and steppers. It has a PIC 16F88 onboard with a bootloader. This is the Nano18 processor. It has a free powerful BASIC, run from a Window's GUI IDE called Studio. This allows you to create powerful control programs that go beyond a mere hand controller, but could be that simple. Demo code for different motor types is available at the BasicMicro(.com) site and in the forums there and at the Lynxmotion robotics forums. Your handheld box could just be a potentiometer wired to one of the unused stepper pins, the driver board and programmer, a power-on LED and a 6V battery holder.
Beyond the PIC's straight control of servos, the other more powerful driver chips onboard are the ULN2803, the L293 and four MOSFETs. The 2803 allows stepper and DC motor control at 500mA per channel; the L293 is a simple half-bridge controller capable of 1Amp per leg; and the FETs will handle 9 Amps EACH! This one board will handle just about any motor situation you care to mention. And if you don't use the stepper motor pins, they are available for analog and digital input/output.
Take care.
kenjj