https://play.google.com/store/apps/details?id=com.sky.altimeter&hl=en&gl=us
Altimeter Variometer (Wear OS) - Apps on Google Play
wear oson googlealtimetervariometerapps
https://play.google.com/store/apps/details?id=com.jonathanVARIOMETER&hl=en
Variometer-Sky Land Tracker - Apps on Google Play
Flight instruments is expensive, but your phone also can be expensive equipment.
sky landon googlevariometertrackerapps
https://www.banggood.com/Matek-CRSF-PWM-V10-CRSF-to-PWM-Converter-w-or-Variometer-10CH-PWM-Output-for-TBS-CRSF-Protocol-2_4GHz-915MHz-868MHz-433MHz-Receiver-p-2002270.html
Matek crsf-pwm-v10 crsf to pwm converter w/ variometer 10ch pwm output for tbs crsf protocol 2.4ghz...
Only US$11.99, buy best matek crsf-pwm-v10 crsf to pwm converter w/ variometer 10ch pwm output for tbs crsf protocol 2.4ghz 915mhz 868mhz 433mhz receiver sale...
https://variometer.app/
Variometer | Vertical speed for flying
Variometer is an iOS app for flying
vertical speedvariometerflying
https://hackaday.com/tag/variometer/
Variometer | Hackaday
variometerhackaday
https://hackaday.com/2009/10/10/diy-cell-phone-alti-variometer/
DIY Cell Phone Alti-variometer | Hackaday
Oct 10, 2009 - [Vlad-Andre] used some of his free time to build an alti-variometer. He does some para-gliding near restricted air space and wanted a backup altitude warning...
cell phonediyaltivariometerhackaday