Point by Point is propbably what you want. If you don't have 6.1 there is a Point by Point toolset. The toolset comes with LabVIEW RT, so if you are thinking of using a Real-time system you'll have it. Incidentally, Real Time might be something to look into since determinism might be important for your applicaiton.
Since your acceleration is going to be a varying with time, you need more than one data point in order to get a proper integral, which is why the integral function requires more than one point. If you only fed it a single point it would have to assume that the acceleration function was constant. The point by point VIs allow you to feed in a single point at a time because they maintain a history of the last several points. If you want, you
can design your own VIs to do the same thing. This is usually done using unninitialized shift registers.