If an Iranian-made Fajr-5 rocket with a 175kg payload of high explosives was whistling over your head, leaving a plume of smoke streaking across the sky, how would you like to hear about it first? For some Israeli citizens, it's a message arriving on their phone, containing a single word: "Yo"
When Israeli developer Or Arbel designed and wrote his app Yo in under eight hours last month, nobody knew quite what it was useful for. Yo is a messaging app with only a single function: it can only be used to say "Yo" to your contacts. Billed as "The simplest & most efficient communication tool in the world," the app has garnered a cautious $1 million (£586,000) investment from venture capitalists, despite its ridiculous concept - but now people are actually beginning to find uses for it, and fairly complex uses at that.
According to The Times of Israel, a pair of developers are now using Yo as a way to alert people of rocket attacks by militant group Hamas occurring throughout the country.
As tensions rise between Israel and the militant government of Hamas in Gaza, rockets are continuing to fall on the capital Tel Aviv and Jerusalem, and a number of services have cropped up to warn people.
Users subscribed to the Red Alert: Israel account will get a simple "Yo" message whenever a rocket is incoming.
Israeli startup owner Menachem Pritzker tweeted yesterday: "Another one of those days..." alongside an image of all the Red Alert "Yo" messages he'd received.