You should be able to instal a heat pump capable, programmable thermostat in place of the one controlling the heat pump now. It would be a matter of figuring out which of its wires to connect to the W terminal that activates the gas furnace. All the furnace controls would also need to be connected to the common from the transformer feeding the heat pump controls. If the heat pump isn't using the furnace blower as its air handler, you will need to run wire between the 2.
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programmable Thermostats