I am using Fitbit and Basis is what I really need. I think by next year we will have something along the lines that Basis promised.
And I can't really knock Basis on the hardware score; the device itself is actually quite nice, from build quality to resilience to battery life. Their web UI's not bad, too, but what I really need is an API to pull that data out and integrate it with everything else I'm logging, and it just doesn't seem like they give a damn about publishing something stable, nor as far as I can tell have they ever.
On the whole, I'm pretty equivocal. On the one hand, the Basis device is excellent, and while I can't speak to accuracy, it's quite precise. On the other, the software support isn't sufficient, and the organization doesn't give any indication of being motivated to fix that. I'm not sorry I spent $200 on a Basis band, but you might be; think it over carefully.
Unfortunately, there's no good API (and your choice of three variously lousy ones [1]), and it syncs in the same way as the Beddit does, i.e., via Bluetooth to a phone. (Or via USB to a computer, but that's not much more help.)
I've thought about trying to MITM the data on its way out from the PC to Basis's sync endpoint, in order to see whether I can trap it there instead of having to query it back out of one of Basis's various APIs once it's synced. On the other hand, I've already got > 1 month of data synced, so I'm going to need some method of extracting data from their backend in any case. (But on the third hand, since Intel bought Basis and Basis apparently doesn't bother much with new development any more, I figure it might be handy to have a backend for sync data in case the hardware becomes otherwise useless.)
[1] Two equally undocumented and unstable not-really-supposed-to-be-public APIs, for which various clients exist on Github in various states of disrepair, and a third, also undocumented but probably more stable, API which feeds their web UI..