Does this work on Quest standalone?

Short answer: no.

Long answer: technically, yes. The ability to run owoTrack on Quest standalone is possible, however most developers have not integrated any form of owoTracks protocols, or even full body in general into their apps. This includes VRChat. Some apps however, do have limited support for things such as slimevr (and hence, owoTrack), such as VRWorkout.

Can I use this with the phone sideways instead of upright?

Yes; you can use it in a different rotation to its intended rotation, however some sensors (such as the magnetometer) may not behave as expected like this. To do it, you have to change the rotational offsets in owoTrack's advanced settings, or use SlimeVR and its device rotation settings.

Is it okay to put the phone in a pocket? Will it work well?

No; a pocket allows the phone a lot of free space to jiggle around in, which may throw some sensors off. It is also advised against putting the device on the thigh/leg, and is preferred to have the device at waist height or above. You should use something like a belt, or a trackstrap to keep the phone firmly in place. (See troubleshooting/drifting for more information)

Can I use multiple phones?

Yes; multiple phones (or dedicated Slime sensors) works exceptionally well for its price, assuming you have functional phones laying around, or found for very cheap. You can NOT use the owoTrack software for this however, you must use the SlimeVR software, found here.

Will 3 phones work?

No; not if you want to track more than 1 leg with SlimeVR. If you do use 3 phones, you will get "Minecraft Steve syndrome", where the legs will behave like the legs from Minecraft.

Does owoTrack support smart watches?

Yes and no; WearOS watches (so Samsung and new Google (FitBit) watches) are supported, however older Samsung watches (such as Tizen) are not suported. Nor are FitBits, Mi Bands, Apple Watches, or any other form of watch if it does not run WearOS.

You can find out if your watch is supported here.

Could I use this on Quest standalone via VRC OSC?

Yes; it is entirely possible to do this, however, the software does not seem to exist for this yet. Feel free to change this if you have the knowhow.

Can I use this to track my 3DOF headset?

No; owoTrack and SlimeVR are both applications for 3DOF devices. You can't use 2 3DOF devices to get 6DOF positions, you need at least 3, and even then, you will not be able to walk around the room.

The phone only contains rotational info. It can't find its position in space accurately, and will drift exponentially once it does start drifting. This means every second, it will double how far its drifted.

Can I use this with a Kinect?

Yes; you can use either KinectToVR (recommended), Amethyst (in beta), or Driver4VR (not recommended). You only need to disable the hip/waist tracker, or in the case of Amethyst, you can connect the device directly, to override the Kinect's rotation.

I'm not sure if my device will work, how do I check?

You can check if your device will work by visiting GSMArena, searching for your device, and checking its sensors.