Check out GE's youtube video below on how their needle guidance software works. We've not had personal experience of the device and software but it looks really good!
An abstract from their webpage:
"The Venue 50 ultrasound system with Pinpoint GT needle guidance software, a high-frequency L12n-SC linear transducer with integrated magnetic sensor – work in conjunction with the Pinpoint GT needle. The Venue 50 detects the orientation of the needle and displays the needle position and trajectory, in plane and out of plane, deep and shallow."