Given iOS's limited support (by design) to 3rd party apps launching other applications, No. Theres no way for a bluetooth device to tell the OS to launch a 3rd party app.
It is possible, but not supported by MS, for the Band to Launch Siri on the phone. It isn't possible to relay voice to siri via the Band.
Don't expect iOS to ever support a feature like this on the Band, unfortunately.
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