In reply to Presley Whippet:
I bought one last year when I was having a few elbow issues, as I've had sporadically over the last 20 years of climbing .
Though the Armaid and other rehab exercises I had the best recovery I've known so to me it was definitely worth the investment. Also no issue in a long time possibly because I still use regularly.
If you didn't want to buy one you could potentially get similar effects from a small massage ball for probably less than a tenner?