One of the things you will need to deal with, regardless of how you make the messages unique, is sending just one tweet when a switch is pressed. To do that, you need to detect the transition from released to pressed. In order to do that, you need to know the previous state of the switch. You have no variable(s) to record this, and no code to record the previous state(s).
int currState;
int prevState = HIGH;
void loop()
{
currState = digitalRead(somePin);
if(currState != prevState)
{
// A transition occurred
}
prevState = currState;
}
Where the comment is, you would put code to determine which transition occurred (released to pressed or pressed to released). That is easy enough to determine. If the current state is pressed, the transition was from released to pressed, and it's time to twit. Otherwise, the transition is from pressed to released, and you don't need to do anything.