Unistroke recognizer are super easy to write and a nice little afternoon project:
Take the time derivative of the trajectory, and ignore it until it's "large"
Once it becomes "large" normalize it to one of 8 directions (N NE E SE S SW W NW) and push the direction into a list then repeat until the derivative becomes "large" in a new direction or you stop getting input.
At the end you have a string you can look up in a table to get the character.
EDIT: after reading the comments apparently the algorithm PalmOS uses is slightly different.
Take the time derivative of the trajectory, and ignore it until it's "large"
Once it becomes "large" normalize it to one of 8 directions (N NE E SE S SW W NW) and push the direction into a list then repeat until the derivative becomes "large" in a new direction or you stop getting input.
At the end you have a string you can look up in a table to get the character.
EDIT: after reading the comments apparently the algorithm PalmOS uses is slightly different.