Getting mobile wallets working seamlessly & instantly is #1 priority for Zcash.
Second priority is getting all dependencies unblocked asap Zcash Shielded Payments by jarys · Pull Request #2472 · trezor/trezor-firmware · GitHub. Getting Trezor dev all the help.
for this to work, you’d need a zcash node as a service that would notify your mobile wallet when a payment is received. It’s probably a good business if someone can offer such service + wallet integration for a small fees