We use UsinligO down here in Bristol -
https://usynligo.no/races - a bit similar, in that you have to run around a bit to get the app to "sing". And i agree it's not the same as finding the flags. In fact, it's a bit crap, cos as soon as the phone app starts "singing the song", I just get out of there & head off on next leg - whether or not I've really "been" to the control feature or not. Hmmm.
Nothing's as good as real O so we make do in the meantime.....
iPhone Charlie? ;-) (great cameras on them......)