Flight controllers

Using a battery, switch and motor alone would lead to long flights and loss of models.  Capacitors can be used instead, but the power decay is set in hardware.

A number of flight profilers exist,  the Zombie  was probably the first. Flight parameters are adjusted via potentiometers on the board.  Other devices, such as the  Tempo   use a mobile phone app or a small device to send a flight profile to the model. Early termination of the flight is also  possible. 

Dethermalisers (D/T)

These are devices for bringing a model down swiftly, usually by tipping the tailplane. This can prevent loss of a model or keep it away from roads/trees etc. I would wholly recommend radio D/Ts, that allow you to choose when to bring the model down. There is a whole article on types of D/T and their installation.