Portable trailer guidance system

1. A system for aiding an operator of a vehicle connected to a trailer with backing up the trailer that is suitable as a customer installed, aftermarket system comprising:

a sensor to measure a rotation of a steering wheel;

an attaching mechanism to attach the sensor to the steering wheel, the attaching mechanism selected from a group consisting of: straps Velcro®, flexible plastic, a steering wheel cover, a gripping device comprising a first point of contact to the steering wheel and a second opposing point of contact to the steering wheel, and an attaching mechanism that can be installed or removed using only one's hands;

an angle sensor to measure an angle formed by a connection between the vehicle and the trailer; and

a computing device to determine a prediction of a portion of a path that the trailer will follow while backing, wherein the sensor to measure the rotation of the steering wheel and the angle sensor to measure the angle formed by the connection between the vehicle and the trailer are not integrated within the vehicle.

2. The system of claim 1 , further comprising: wireless communications circuitry to communicate steering information about the vehicle to other parts of the system.

3. The system of claim 1 , further comprising: a power source not wired to the vehicle.

4. The system of claim 3 , further comprising: one or more batteries, wherein the one or more batteries are either rechargeable or disposable.

5. The system of claim 1 , further comprising: one or more devices selected from a group consisting of: a pendulum, a rotation sensor, an accelerometer, a gyroscope, and an IMU.

6. The system of claim 1 , wherein the sensor to measure the rotation of the steering wheel further comprises: a surface that when placed across the steering wheel will self-align the sensor to be in the plane of the steering wheel.

7. The system of claim 1 , further comprising: an attachment mechanism to attach the sensor to measure the angle formed by the connection between the vehicle and the trailer to the vehicle proximate to a hitch ball.

8. The system of claim 7 , further comprising: a stretchable or flexible cord-like device between a first cord mounting point and a second cord mounting point, wherein the first cord mounting point is on the vehicle end of the flexible cord-like device and the second cord mounting point is on the trailer end of the flexible cord-like device.

9. The system of claim 8 , wherein the connection between the vehicle and the trailer comprises: an axis of rotation, and

wherein the first cord mounting point is located at a first distance from the axis of rotation and the second cord mounting point is located at a second distance from the axis of rotation.

10. The system of claim 9 , wherein the first distance is equal to the second distance.

11. The system of claim 7 , further comprising: a movable joint to correct for up-and-down motion or pitch of the wheels of the trailer relative to the vehicle.

12. The system of claim 7 , further comprising: a movable joint to correct side-to-side motion or rotation for the trailer wheels not being level relative to the leveling of the vehicle.

13. The system of claim 7 , further comprising: a wireless connection for communicating information about the connection between the vehicle and the trailer.

14. The system of claim 13 , further comprising: one or more of a Bluetooth® communications link, a Wi-Fi™ communications link, a ZigBee™ communications link, or an RS-232 communications link.

15. The system of claim 1 , further comprising: displaying the prediction through one or more devices selected from a group consisting of: an LCD display, a smart phone, a tablet, a lap-top computer, a back-up camera's screen, a device running the iOS™ operating system, and a device running the Android™ operating system.

16. The system of claim 1 , further comprising: a button to do one or more of (i) powering-on the sensor, and (ii) providing a user input.