Andvik, Erik. Tshangla. 2003. wals:206
"A high/low tone contrast is evident on some sonorant initials even in some Bhutan dialects". The Padma-bKot dialect, spoken in Tibet, has completely transphonologized initial voicing into a tonal contrast.
At least one glottalized sonorant final is present, but the source doesn't give details beyond that.