Personally I would get a glucometer as soon as possible and start learning to test at home...It has saved both of my diabetics on numerous occassions even with all the years of experience I have with feline diabetes. In fact with Maxwell it is probably the reason he is still with me, you see I adopted him as a diabetic, so I had no clue what normal behavior was for him. He spent 2 weeks in foster care while transport was arranged to get him from Boston Mass. to me in Hastings Nebr. He was started on 1u twice a day and at the same time had his diet changed from dry kibble to all low carb canned. Well I gave him 2 shots total on insulin one shot at 1u and the second at .5u and he started testing in normal range and has been in remission and off insulin now for 2 years as of this last November 1st. If I had continued to shoot him blind I could have very easily sent him into hypo or even killed him.
There has also been more than once that Autumn has been crying at me for food, I always test her before I feed her, on several of those times she has tested in the 20s without any outward signs of hypo. Plus by testing her at home I have been able to reduce her dose from 1.5u to the mere .5u she is on today, and with any luck at all She will let me know when she needs to go down in dose again and hopefully one day she too will be in remission and diet controlled like Maxwell.
You do not need your vet's permission to test at home, you don't even have to tell her that you are. But as someone that has diabetes in her family I can tell you no human diabetic would inject insulin without testing themselves first, so why should it be any different with a cat?
As far as what to look for any human glucometer will do as long as it takes a small sample of blood and the test strips fit your budget as they are the most expensive part. A very popular brand around here is the Walmart house brand called the Relion of which there are 3 models that are used around here, the confirm, the micro or the new prime. In fact I have the Relion Micro as my back up meter for Autumn it was originally Maxwell's. I also have a Bayer Contour that is Autumn primary meter since she is a DCIN (Diabetic Cats in Need) sponsored cat and they supply her test strips.
The other things that you would need to get started on home testing are the lancets (28-29 gauge to start with)
A lancing device to fit the lancets.
Something to back the ear for poking ( I use a folded up paper towel)
A rice sock (a thinnish cotton sock with about 1/4 c of plain uncooked white rice in the toe and knotted) or some other way to warm the ear.
Low carb treats for Ruben for each test regardless if you get blood or not. He will quickly figure out that a small poke in the ear is worth the yummy treat and the extra one on one time with mom.

Autumn actually comes hunting for me if I'm running late on a test time or she will beat me to her test spot and be waiting.
That is pretty much it...you can google Testing a diabetic cat and come up with tons of videos to watch. It takes some practice but once you find your groove you can do it in your sleep and many of us have...lol
Mel, Maxwell, Autumn & The Fur Gang