A balloon cannot take very much pressure inside but pneumatic tires have pressures in the range you mention. There are battery operated tire pumps that could be controlled to make the pressure go higher, with a solenoid valve to let out air to decrease the pressure. An Arduino can activate either of these depending on the pressure setpoint you want to maintain (measured with a pressure transducer).
If your system is always above ambient conditions, all you need is a small heater to raise the temperature to your desired temperature. Filament type lightbulbs can readily heat small areas to the temperature you mentioned.