Handwritten character recognition as characters are being traced I'm looking for an OCR technique (PCA or SVM or anything else) in a peculiar setting. I want to detect the motion of the finger so that if someone writes something in front of the camera in the air, I want to recognize the characters online (meaning as soon as they are written).
There is a paper "Using Mobile Phones to Write in Air". It basically uses the mobile sensors and machine learning to detect words. The Results show that English characters can be identiﬁed with an average accuracy of 91:9%.

There are some open source projects like "hand-gesture-detection" on Google code. I think you can use them as the start for your project.