Has anyone experimented with DIY ECGs, pulse oximeters, making your own medical "toys"?

I have always been curious about the tech people have been using. Downloaders, video processing software, search engines, AI tools, perhaps local AI stuff? In terms of hardware, has anyone experimented with DIY ECGs, pulse oximeters, making your own medical "toys"?

I actually once built a very primitive ECG, just consisting of a couple of OP-Amps, a couple active filters and one could see the typical signal on a scope. It was even possible to measure various parameters of the QRT complex (QT time and so on). Of course it was far from anything a real doctor would use, but it was interesting to see.

If you are interested there are even some dedicated integrated circuits, like the AD8232 from Analog Devices, for ECG measurements. That particular one is even available as a module on ebay (probably just the simplest circuit one can build with it from China).

It would be interesting, though, to build more special equipment...

Due to losing a court case the newer watches have the function disabled but Apple Watches series 9 and before can run an ECG check your blood pressure pulse etc . It will even tell you any variability in heart rate ( I happen to have congenital long QT ) so being able to have my watch track that is helpful ,my current heart rate variability is 16 ms . I know most are guys but for women there’s period and fertility tracking if you want to use it .nothing wrong with my series 5 ordinarily I don’t find I need the latest however last Black Friday I was able to purchase a series 10 for $180 my series 5 requires multiple daily charges my series 10 brought Fall detection ,crash detection 1 hour of charge gets you 90% charge , also if it matters to anyone with the new watch charger it will charge your watch phone and EarPods . So I use my series 5 for my heart and sleep tracking and my 10 fall and crash detection has been a lifesaver ( I fell in July ,thank god my face caught me (LOL)seriously by the time I regained consciousness FD was coming thru the door , I spent 2 weeks in hospital on that one .anyway you can pick up a used older Apple watch and keep in the fetish stash.

@DoctorGyno I also experimented with opamps and tried a very very simple analog circuit but I ended up amplifying the noise from the air more than anything. My goal was/still kind of is, to build something, that would at least produce a pulse so I can trigger a led/buzzer with each heartbeat. I've got the classical set of suction cup electrodes + 4 limb ones so I wanted to put them to good use.

@Clinic_Boy You need to filter out that noise if you want something useful. First, try to get AC-coupled with a very-low cutoff frequency (e.g. 1Hz), then a lowpass to get rid of all the hum from the grid (50/60Hz). If you do that, your signal is gonna be much better

I have an Echo CORE 500 digital stethoscope. It's not an EKG, but much like telemetry, it uses AI and algorithm to interpret what it hears, and has a display screen on the scope. It's not perfect, but a decided advancement in technology.

https://www.youtube.com/watch?v=Y0vTmtGVBf0