Distance sensing with comparator
In order to bring order out of chaos, I enjoy looking at older questions and helping them to completion. This question, along with the good contributions from the above commentors can be moved forward to help others :

Using the IR sensor as described, I have merely modified the OP's circuit so that the stated function can be implemented. 

As stated by comments above, low power op-amp needs a transistor to be able to drive the "vibration motor". Transistor Q1 has been added. Use any transistor that has V-gate threshold less than 4 volts, along with minimum Id of 100mA. 

LM393 output is open collector, thus the addition of R1.

R2 was added to put some hysteresis into the circuit, so that the op-amp output doesn't oscillate (bang bang, go hi then low) when sensor signal is close to the setpoint.

Setpoint is achieved by the potentiometer.

The circuit proposed is not supposed to be an exact solution, but one that will give a starter point for others.