The SparkFun Current Sensor Breakout is a High Precision Card that uses the ACS723 for Moderate AC and DC Current Detection Applications. The ACS723 Sensor uses a Hall Effect Sensor to Emit a Voltage relative to the Current that flows through the IP + and IP- Pins on the Board. The advantage of using a Hall Effect Sensor, specifically, is that the Circuit Being Detected and the Sensor Reading Circuit are Electrically Isolated, which means that although your Arduino is Operating at 5V, the Detected Circuit may be Operating at Higher DC or AC voltages.

Electronic Brick - Sensor de Corrente - Loop 4-20mA

Bi-directional Logic Level Converter 4-channel by I2C BSS138

The Current Sensor 70A is a great option for those looking for equipment to measure current up to 70A and that is non-invasive.