Fully working HEAT wallet for HEAT transfers and messaging in the decentralized p2p network has been available for a couple of months:

https://heatwallet.com/
https://github.com/Heat-Ledger-Ltd/heat-ui/releases (installable client, for both thin client use and full node use)
https://github.com/Heat-Ledger-Ltd/heatledger/releases (installable server for full node)

HEAT API guide and interactive test API:
https://heatwallet.com/api/