Actually, the current provides info about the torque.
To measure the speed, you need to measure the back emf.
You could measure the voltage across the motor and subtract the voltage drop across its Ra (Ra*Ia) to get the back emf. You need to know Ra and Ia is the current you measure.
The drawback is lots of calculation and the fact that Ra varies with temperature.
The best way would be to measure the back emf directly, by using a chopper for the motor voltage and measure the back emf when the switch is off.