Satellites are extremely expensive pieces of kit, even without the cost of launching them. A modern telecommunications satellite can cost billions of dollars. Unsurprisingly, their owners want them to keep functioning for as long as possible, however they have to maintain the right orbit to be useful, and as soon as they run out of fuel, their orbit will slowly start to change until they are useless. Satellites are solar powered and built to last, so that most satellites finish their lives perfectly serviceable, but just in the wrong place.
A company called Vivisat is hoping to change this: they have designed a relatively small spacecraft called a Mission Extension Vehicle or MEV, which is powered by efficient ion thrusters. The idea is to fly the MEV up to the satellite, dock onto the motor which every geostationary satellite uses to get into circular orbit. The MEV then takes charge of pointing the satellite and keeping it in position, allowing it to keep working for several extra years.
This is another example of space starting to be used in a more innovative way, which hopefully will lead to exciting things in the future.