If you have an iPhone, you could use that in conjunction with something like Reincubate's Camo. There was an interesting discussion about it on HN recently [1]

If you have an iPhone, you could use that in conjunction with something like Reincubate's Camo. There was an interesting discussion about it on HN recently [1] [1] https://news.ycombinator.com/item?id=25869460 https://news.ycombinator.com/item?id=25869460