It's payback time in Downtown Cairo; German Art Company, VR/Urban, are giving Cairenes a shot at revenge for the incessant messages and adverts we are bombarded with everyday in this city. Be it flickering neon names, indictments of 'Yala!' from soft drink companies, or even the coy gaze of Nancy Agram tries to muscle in on our decision-making. The latest visual arts show at D-CAF reclaims the streets for the people, handing them a slingshot, and offering up the cities walls as their canvas, to paint the town with what they have to say.

Not that Cairo has ever been short of people taking to its walls to voice an opinion; every available space is littered with graffiti by artists making themselves heard. However, using a digital catapult – all in the name of art – turns out to be a lot more fun, plus, it's guilt free for those of us in a law-abiding frame of mind.

The clever people at VR/Urban have come up with a visual art piece based on the weapon of choice for cartoon schoolboys – the slingshot. Amidst the dusty Downtown street cafés, this weekend, one wall of the towering Egyptian stock market is being transformed into a projection space for the project. The device is wooden and wireless, featuring a phone keypad into which a message can be typed in the Arabic or Latin alphabets. Users also have the option of changing the colour of their 'paint' background, and then using a lazer to pinpoint the spot onto which the message will be splattered. After that, it's just a matter of pulling back the elastic and releasing, to fire the digital message through the ether, and have it projected onto the wall above.

Along with the classic 'I was here' messages, people took the opportunity to big up their favourite football teams, share a treasured quote, or even profess undying love. After a while, attention turned to political messages with the president's name featuring more than once, and respects also being paid to those who died in the revolution and football violence. In truth, the messages were very similar to those painted around the city, but by providing a space for people to come together and express themselves all at once, SMSlingshot provides a space for dialogue, where groups can exchange views and discuss, rather than just stating their opinion. In any case, it was a great conversation starter, with our favourite slogan reading 'I hate Cairo Scene', which we categorically deny slinging.

Passersby who happened upon the event took to the task avidly, with young and old all clamouring to try out the fancy bit of kit. The equipment doesn't take long to get the hang of and once you do it's pretty addictive. The 'paint' makes a satisfying punchy noise as it hits the wall and then trickles down. After a few minutes, the message becomes lost under new ones, or fades to nothing, symbolising the speed of flow in social media today. Just as social media allows public opinion to rise up and be heard, here VR/Urban gives them back the streets to make their mark on.