It may be hard to keep your coffee hot all day with a thermoflask or a heater. I suggest to fix a heating element inside (5W in this case) a mug with the wireless power module.All the circuit has to be then sealed away so that they want be affected by liquids.But the top side must be able to transfer heat.
In the otherway if we can connect a peltier with a mechanism to change side cool coffee can be also served yourself as you wish.
- FT1235 wireless power Transmitter and the receiver kit
- 5W heating element