Your phones will, in fact, serve as a cryptographic money wallet that will be linked to your current data (phone number/Facebook). BillG Coin's blockchain, like any other public blockchain, will allow in-application/outer wallets to hold BillG Coin and execute with it by directly submitting exchanges to the blockchain.
This is a benefit that we have already scheduled for the task's Stage 3 stage. (As an update, we are currently in stage 1 - cash distribution - we will then send a Testnet as stage 2, and step 3 will be when our mainnet goes up.) You will also have the option to take full responsibility for private/public keys during stage 3 of the project.
BillG Coin seeks to be more accessible to the general public, which is why we're aiming to create this integrated interface. This tiered execution was chosen to make it easier for regular people to use. We're still in the early stages, but we're excited about the road ahead of us.