The txOut port. Where information from your elm app is sent OUT to javascript land. Used for sending Send Tx parameters to Metamask, or other wallets.

port txOut : Value -> Cmd msg

The txIn subscription. Where information from the outside comes IN to your elm app. Used for getting the TxHash response from Metamask, or other wallets.

 port txIn : (Value -> msg) -> Sub msg

onSign : Message after metamask/wallet has signed tx and returned tx hash
onBroadcast : Message after tx is confirmed sitting in tx queue on the node
onMined : ( message after tx is mined,
            (number of blocks deep to watch tx, message on each mined block after tx is sent - stops sending messages when first tuple value is reached)
          )

For checking whether a tx has reached a certain block depth (# of confirmations) in a customSend

Look into the errors this might cause, some kind of cleanup process should probably occur on changing a node.