This is very dangerous and could easily make your tello fly away! You have been warned!
TelloAltLimitSetter by keiji matsumotohttps://itunes.apple.com/gb/app/telloaltlimitsetter/id1382095075?mt=8
FREE version for windows!
connect pc WiFi to tello
set altitude limit
FREE android version
I SUGGEST NO MORE THAN 15 METRES! You have been warned!