Nancy-
I don't have any gadgets to recommend, but I just want to chime and give you a cheer of support as another person who can understand somewhat your experience.
I've had to have surgery three times in the past three yrs, each with a long recovery and significant restrictions. it's extremely frustrating to go from a high level of fitness to zero. Well, it's not really zero, but it might as well be since we Cathletes are used to being über-fit, and having to work hard to regain something you've already achieved and then lost through no fault of your own just plain sucks. For me, each time coming back has been like clawing my way out of a deep well. There were times I was so frustrated I cried. BUT, each time I HAVE come back and I've come back faster than I thought I would when I first started trying. Personally, my cardio and lower body strength comes back first...I have to work longer to regain my core and upper body strength.
Do whatever it takes to keep yourself going. Since you know you like gadgets, go for it. Do anything that makes you feel closer to the old you. It might also help to promise yourself prizes as you move forward (e.g., the first time you can do a Cathe workout, then the first time you can do a Cathe workout without pausing, then the first time you can bang out your favorite hard Cathe workout). Heck, give yourself a reward for just plain doing it!
FYI, I do have a hr monitor and sometimes wear it during spinning. I use it to make myself work harder when my legs are tired but I can see my heart can take more. I don't do this with any other type of cardio, where I just go by how my body feels. oh, and I used my hr monitor for the exact opposite purpose when I was firsts able to return to spinning (making sure I wasn't pushing it too hard).
I wish you the very best. As a Cathlete, it's clear you're willing to work hard and enjoy a good butt kicking. You'll be back before you know it!