Limitations of Bluetooth data transfer

So I'm not 100% sure if this is the proper place to ask this. I'm working on trying to make a simple HUD in some glasses, the hardware side I'm okay with. It's mainly the software side because it's a bit out of my realm. My premise is hopefully get an Arduino compatible chip with a Bluetooth chip on it, which I can just connect to with my phone, then have the arduino print out some basic info like the phones battery percentage, maybe direction (NESW) from the gps.
I took about 4 years of data structure based programming and have worked a bit with the basics or arduino so I'm fine with that. My main issue is I've never worked with bluetooth signals, when I did research into this project I noticed just about everyone made an app for their phone to work with their setup. I'm hoping that since all I'm trying to get the arduino to do really is receive serial outputs, not make calls, send texts, or any of that, that I can avoid having to make an app and just pair it as though it were a pair of Airpods.
My question sort of is, is this a crazy assumption? I've been searching around online as to what exactly can be sent via a bluetooth connection but have come up empty. Does anyone have any direction to point me in to figure this out? I feel like if the phone can send music via bluetooth, i could just have the arduino run a function like .getBattery/.getDirection/.getUnreadMessages and have serial responses like "74" "W" "2" without the need of creating an app. Any help appreciated

My question sort of is, is this a crazy assumption?

It is certainly a little hopeful. Something running on the 'phone is needed to send the data, either at intervals or on demand. The actual reception and parsing of the data, which will appears as a serial data stream to the Arduino, is easy

I was afraid so. I know on Samsung you can read the battery level of devices from the Bluetooth tab, I was kind hoping I could do the same with the arduino based on the phones levels, but yeah I'll more than likely have to look into developing a widget or app to send that data

York090:
I'm trying to get the arduino to do really is receive serial outputs,
My question sort of is, is this a crazy assumption?

It most certainly isn't. You are probably about the ten millionth person to want to do this - or something like it. All you have to do is get the phone to transmit the data you specifically want to receive. This probably goes some way to explain all that reading you have done about people making their own phone apps. Anything you care to send can be received by Arduino, it just needs to be a serial stream, properly formatted, and can hardly be anything else. This is not an Arduino problem. Your hopeful hardware premise has already been fulfilled, probably several times over.
I reckon what you want to do is quite feasible but you are looking in the wrong place, and trying to do something that specialised without making a specialised app is pretty fanciful.

Have you looked on google play? this is an example of an Android app that can send NMEA strings/gps data to bluetooth https://play.google.com/store/apps/details?id=com.meowsbox.btgps Bluetooth can be frustrating sometimes though to get both ends paired and connecting....

azeo:
Bluetooth can be frustrating sometimes though to get both ends paired and connecting....

I submit that is alarmist nonsense. The whole point of bluetooth is that the dumbest user can use it like an expert - which accounts for its success.

Note I said sometimes, I have just spent the best part of an hour cajoling an Android app to reliably talk to another Adroid device running a variety of bluetooth terminals with limited success, whereas connecting same app to an ESP with a BT module no problem at all. It depends on the context...

OP, this might also be of interest to you, found it today, works nicely SensoDuino: Turn Your Android Phone Into a Wireless Sensors Hub for Arduino : 11 Steps (with Pictures) - Instructables , can send a variety of sensor data off to bluetooth, but not battery unfortunately.

Nick_Pyner:
I submit that is alarmist nonsense. The whole point of bluetooth is that the dumbest user can use it like an expert - which accounts for its success.

I concur with my learned colleague, m'lud. BT is ridiculously simple. Cheap too.

Ain't hard to write an app that communicates with an Arduino via BT.

BT doesn't have a great range -- 10m

John.

The BT Module send and receive bytes data, and in programmation every things is bytes, so, you can, how?
I think that you need a App (Android Studio, Flutter, etc), in the first place you must make it on Android - Arduino with the app, after, you can try directly.

"I know on Samsung you can read the battery level of devices from the Bluetooth tab"

Is this reading the Samsung battery level on another device, and on what device is the Bluetooth tab?