I spend a lot of time when I am ‘playing radio’ in places that have little to no mobile phone service. This is both a blessing and a curse. It means that it likely means I am in an RF quiet environment from 3-30mhz on HF, however should I want to tell my non radio friends that I am running late but not to worry, or I want to check what repeaters are around me - then I am out of luck.
There is a data mode called Automatic Packet Reporting System (APRS) - when it was created it was designed as a ‘intelligence gathering tool’. If you were plonked in another city with only your radio and a Terminal Node Controller (TNC), within 10min or so you could gather all you needed, from repeater information, local radio nets and know how to contact nearby stations in simplex as well as send 2 way short text messages. As time has gone on it has sadly fallen away to mostly be seen as a tracking device, showing where different stations are.
Just some of the fun things OTHER THAN TRACKING that I have found out is possible.
Spend spots for SOTA Activations by APRS Messages https://www.sotaspots.co.uk/
Check and send emails via APRS https://www.winlink.org/APRSLink
How do I use APRS when I am portable?
I always carry a small Android Tablet with me when I am operating portable for logging or using the raspberry pi for digital modes (http://wadeabout.com/blog/portablepi-a-raspberrypi-for-amateur-radio-portable-opers) so since I am carrying the tablet it makes sense to use APRSDroid app. I connect a tiny match box sized Bluetooth TNC from http://www.mobilinkd.com/ - I have connection cables for all of my radios - my Yaesu FT60R (my primary HT), my back up HT a Baufeng UV5R, and a cable for my FT817ND which all allow connection to the Mobilinkd 2.
This allows me to send location data, receive repeater information, and send 2 way text messages.
Recently I picked up a 1w APRS Radio with built in thermometer and GPS. Essentially is a fully self contained APRS unit.
https://www.aliexpress.com/item/AP510-APRS-Tracker-VHF-with-GPS-Bluetooth-Thermometer-TF-Card-Support-APRSdroid-KISS-Model/32392912633.html it also has bluetooth inside so like the mobilinkd it can be used with the android tablet for 2 way communication, however in stand alone mode it beeps out location data based on your speed and recent movements so to not jam up the single APRS frequency. I had read online that many spoke negatively about its meger 1 watt. I have not found an issue in residential Canberra. (VK1)
If you are still asking what is APRS? Here is a video by the guy who invented it: