Import / create a Wallet from a key with bitcoind or bitcoin-cli to use as a hotwallet? i've created a HD Wallet via (https://github.com/GemHQ/money-tree) 

i would like to take the private key and throw that into my daemon so i can listen on incoming transactions and also transfer the funds to our coldwallet via RPC calls. 

how do i create a wallet.dat via privatekey only so that my daemon can open it?
You can use the importprivkey and importmulti RPC calls in bitcoin-cli to do this.