Training on standby instruments is common in many systems for the training for the IR. And for IFR certification, all authorities I know of require a second instrument from a different power source. For example, if a gyro is air vacuum powered, a second gyro instrument must be powered from a battery.
This second instrument is often a 'turn co-ordinator' which is an instrument developed in America in the era of competirion between manufacturers. It is not only sensiteive to yaw, but roll as well. It may be useful for smooth flying, but it's worse for standby instruments flying than the more traditional turn and slip indicator. This is because the gyro rotates in a different direction and if g is applied, the indication is for less yaw, whereas the T and S indicates more yaw. If you're trying to recover to wings level, it's easier to unload g to get the instrument to read correctly - the T and S is better in this case. One training school I instructed at had the turn co-ordinators repalced by T and Ss for this reason.
As mentioned, training is one thing, but trying it for real in bad weather years after your training is another.