Cape Town communities are turning to technology to keep them safe after two horrific murders. A 48-hour hackathon was held at the weekend to develop Hamba Safe, an app that will connect people so they won't have to walk, jog, hike or catch public transport alone.Elizabeth Senger, communications officer for Silicon Cape, which organised the hackathon, said: "The murders of Franziska Blöchliger and Sinoxolo Mafevuka have caused so much outrage, and then there are all the cases that don't get reported. People are tired of feeling vulnerable to crime."Whether it's recreational running, cycling or a daily walk to a taxi rank, an easy-to-use app is required [to] enable safety in numbers by helping people to connect beforehand."Another community-led initiative is Safety Mountain Tracking, which uses WhatsApp to track hikers in a bid to keep them safe."We have five dedicated monitors who volunteer to keep track of hiking groups. Crime in the mountains is now out of control," founder Anwaaz Bent said.Last year almost 5,000 hikers were tracked, up from about 3,900 the previous year.Other communities in the Mother City have been using a global app called Cell 411, which the developers describe as a "microsocial platform" because it is intended to connect small groups, at street level, within a family, or among people who frequent a common spot.It sends out alerts to notify others in the group if you need help, and tells them where you are and the directions to that spot.Jenni Sterne, a Cape Town single mother, said she set up a Cell 411 group with her two teenage daughters, other relatives and close friends."If one of my daughters was in an emergency and I was not able to get to her, I would feel secure knowing that someone else in our close circle would also be notified even before trying to get the police," Sterne said.Police spokesman Brigadier Vishnu Naidoo said police did not have an app, but the 112 number and Twitter had proved invaluable to the SAPS."On any cellphone network the 112 number is used frequently to call out our flying squad unit."On Twitter, our handle @SAPoliceService, is now followed by 250,000 people and is manned 24/7. When someone tweets us about violence, or a robbery, we pass it on to the appropriate station."..