Yes, I had a quick go I tried a Mike (clapping) and a Guitar and I have to see in my experience it didn't work at all! The tempo was 'wandering' a little bit, but I was going from about 120 BPM to 60BPM to see how it transitioned and what the lag was...but it didn't change dramatically, just stayed around 115-120 BPM.
It wasn't a very scientific experiment- I will try again over the weekend with a known tempo source from one of my drum machines- but the singing/playing guitar in didn't seem to do it for me....maybe it only syncs with a recognisable drum beat?