Activity trackers without online requirement

So I just found about the amazing thing that is QS and I’m browsing through lists of various gadgets on offer. Unfortunately, all the descriptions I’ve read thus far include some variant of “and it syncs with your online account”.

What activity trackers are there on the market that do not rely on some online platform to function?

It’s okay if I have to download some software to allow my PC or phone extract the data from the device, but that’s as far as it goes.

There are quite a few tracking apps that lack an online component (and some are even open-source). Some work with devices that have a standard Bluetooth LE interface (e.g. heart rate monitors), and others just use the phone’s hardware to count steps or do heart rate measurements. Android or iOS?

Out of intrigue; what is the reason for not wanting a device that requires internet connectivity? Access? Data privacy? …

I find it offensive when online connectivity is demanded when not technically required. Most of all though, I want the tracker to output in plain text that I can then import in Excel and do my own analysis.

Oh, and I use Android.