the device is used for detecting leg movement (due to cost and component available, i was only given a vibration switch which will only have simple on and off) and if there wasn't enough movement over an hour, it will warn the user
it will monitor movement using a vibration switch (very very sensitive)
You should be able to do what you want with the components you have available, but it might be worth taking a step back and clearly stating your objectives.
You are trying to warn somebody that they have not moved their leg sufficiently is that correct?
Is the purpose to ensure they maintain circulation to the limb?
How long can the person leave their leg without circulation, I would suggest 10min max.
Therefore there is no point in warning the person after an hour, that is way too long.
Also you describe the vibration sensor as "very very sensitive", will it react to levels of movement less than that required for circulation in the leg i.e. general upper body movement/vibration such as breathing (this should be easy to test just strap it your leg, keep your leg still but breath, move your arms etc.). If the sensor reacts to movement other than just the leg then you will need to be smart in how you use it to ensure circulation is being maintained.
This might be going off at a tangent but have you considered applying appropriate, safe, voltage to the leg muscles to make them contract/relax.
Yet another silly though, I don't suppose the sensor is sensitive enough to detect a pulse