Just getting to the point of testing this item was a nightmare. Shipping was relatively quick but that was the end of any decent experiences with my order.
1. Both product description and box claim it includes a "power adapter" but one was not included. When I contacted support, I went back and forth for several days, in which they tried to give me a $5 refund so I could purchase one myself (despite the fact that 9V adapters cost much more than $5 in my experience) because they do not stock 9V adapters anymore for some reason, until finally relenting and sending me a 6V adapter, which I do appreciate, but it should not have been that difficult, nor should the listing and packaging have included false advertising in the first place. If I had known it did not actually include a power adapter, I would have purchased a different product that did.
2. The batteries included in the package were leaking and corroded, and therefore unusable. After the adapter debacle, I didn't bother contacting support, as it is just not worth it.
3. The setup process once the machine actually turns on is not intuitive, and if you accidentally progress past a setting, there seems to be no way to go back and update it, so you're stuck unless you want to start the entire process all over again.
I have not tested the app yet, but I imagine it'll be a headache like everything else to do with this product. I will probably not bother and will simply track my readings manually.
Once actually getting the monitor set up, it worked fine (on the second try, it errored out the first time). I will keep it as I do not have the energy to deal with a return, but I will not be ordering any more devices from VIVE in the future. When this one inevitably dies, I will replace with a different brand.