With APRSdroid in AFSK (audio) mode, you can transmit data through the radio in APRS mode.
I experimented with two Baofeng radios and here are the APRSdroid settings.

Settings - Options

• Call sign - your call sign, for example R1BJK
• SSID - 15 "General additional stations" or other SSID ("portable station", "Mobile station"). If two radios are used with your call sign, their SSID must be different. For example, -7 and -15.
• APRS path - empty
• Connection parameters:
  • Connection logging - ON
  • Connection protocol - Audio (AFSK)
  • Quality decoder - ON
  • Audio output - voice call
  • Frame synchronization prefix - 400
• APRS symbol - any
• Voice frequency - space
• Comment - space
• Location settings - Enter coordinates
  • Coordinate source - Enter coordinates
  • Latitude: 0
  • Longitude: 0
  • Automatic sending\* - Disabled
  • Minimum update time - 60 minutes (does not affect, because sending coordinates is disabled)
• Location confidentiality - 4 (DD*) (does not affect, because sending coordinates is disabled)
• Transmit Speed & Heading - Off
• Transfer height - Off
• Keep screen on - Off
• Notifications
  • Incoming messages: Flashing LED, Vibration
  • Notifications - Own location packages - Everything is turned off

• If you enable the "Automatic sending" option, the radio station will broadcast coordinates every hour (or every n minutes specified in the "Minimum update time" parameter). This way you can enable the APRS beacon in parallel with the APRS pager. But various options using a GPS receiver ("SmartBeaconing", "send periodically at an interval" or FakeGPS) lead to more frequent sending of coordinates, which leads to a significant drain on the radio's battery, and searching for satellites drains the smartphone. In the article I consider the option of transmitting messages as needed, in “pager” mode. In this mode, the radio station transmits only when messages are entered and sent by a radio amateur - the radio station operator.

Usage

To start communicating using APRS you need to transmit at least one packet. Then another station will be able to respond to the APRS packet.

To initiate an exchange, one of the operators must transmit their location once. This location can have a latitude and longitude of 0.0 / 0.0. Pressing the "Send Location" button with VOX enabled will put the radio station into transmit mode and identify you on the air, giving other correspondents the opportunity to respond by finger pressing at your callsign.

To listen to the broadcast via a cable from a radio station and analyze incoming transmissions (reception) and transmission capabilities, both radio stations and a smartphone with APRSdroid must be in coordinate tracking mode (button "Start tracking"). Information is transmitted over the air only in tracking mode when the APRS service is running on the smartphone. The message “Stop tracking” should be lit on the screen.

Sending APRS parcels is done using the “Messages” pop-up menu, which appears when you hold your finger on a call sign for a long time. The maximum message length is 43 characters (ASCII, letters 0-9, symbols, A-Z, a-z). The APRS message format is described in more detail in the PDF document https://www.aprs.org/doc/APRS101.PDF see "8 POSITION AND DF REPORT DATA FORMATS".

APRS cable for smartphone is called APRS-k1. It is sold on AliExpress and Ozon marketplaces. (Search using the keywords "cable for APRS").