Ridiculous as this sounds, there's a very interesting conversation happening on Twitter with Marc Andreessen about this apps' uses.
Apparently, the "missed call" phenomenon, where people will call someone else and hang up, is incredibly popular, especially in other countries (e.g. Bangladesh). It's a free way to communicate 1 bit of information, which in many cases is enough if the people know beforehand what they want to communicate. E.g., "come downstairs", "call me back on another line", etc.
I think one article mentioned that missed calls are 70% of the traffic of cellular operators in Bangladesh!
When I was in high school our local mobile networks brought out a feature called "Please call me" in which you used USSD to send an unbilled notification for another number to call you - you only got around 20 per day but that was more than enough.
Most people seemed to use it to notify their parents that they were ready to be picked up from a prearranged place much like you're describing with missed calls.
The "missed call" is not a phenomenon. Most cell phone callers (not the receivers) in the developing world are charged by the minute for each call. Hanging up before the call is answered incurs no fee. This is simply a way to save money.
Yo is ridiculous and doesn't necessarily solve any problem that is not solved with existing messaging apps.
Apparently, the "missed call" phenomenon, where people will call someone else and hang up, is incredibly popular, especially in other countries (e.g. Bangladesh). It's a free way to communicate 1 bit of information, which in many cases is enough if the people know beforehand what they want to communicate. E.g., "come downstairs", "call me back on another line", etc.
I think one article mentioned that missed calls are 70% of the traffic of cellular operators in Bangladesh!