ArnoTLE:
Gloves with sensors which sense the type of touch, a highfive should give one point, holding hands should add 5 points to a database.
That's trickier.
Probably the easiest way to do this is based on duration of contact. A high-five makes contact for maybe half a second, a handshake 2-5 seconds or so.
Another option may be an accelerometer, which you use to detect the orientation of the hand (sticking out or sticking up, about 90° difference in angle).