This is a personal preference item. Best mirrors and the Get Out And Look perspective are primary solutions. The camera is additional help, not a replacement. If you can't afford a camera, use the methods that have been used for many, many years.
Note - the very best addition is the eyes of an external spotter. Stop is a very effective instruction. Turn left or right is usually not required if you are doing your job.
Now, as we all get older, we need more help doing what we do. Worth considering.
So, not necessary if you GOAL, but a very nice good to have after you have completed the GOAL exercise.