With this dac, mobile phone developers can send a notification to users without a cental server. This is just a thought, maybe we can discuss more here.
Push Notification DAC == PND.
step 1:
developer ---[register a token from]---> PND
step 2:
users' devices(may an android phone) ---[register device to]---> PND
step 3:
developer ---[send notification with step1's token]---> PND
step 4:
PND---[send notification]--->user's devices