You can use this code (in B4A as well):
Dim bc As ByteConverter
Log(bc.HexFromBytes(Array As Byte(Bit.ParseInt("1011", 2)))) 'will print 0B.
bc.HexFromBytes is in most cases better than Bit.ToHexString (which is not available in B4i) as it writes each byte as two characters adding 0 if needed.
You can add .SubString(1) if you want to get B instead of 0B.