Facebook spies on us\u00a0all the time, and, by extension, so do the companies it owns like\u00a0Instagram\u00a0and\u00a0WhatsApp. Now, one app is turning the tables by letting you use all that data they\u2019re quietly collecting to spy on your own WhatsApp friends and contacts.\r\nChatwatch\u00a0takes advantage of WhatsApp\u2019s public online\/offline status feature, which lets your friends know when you\u2019re readily available to talk. Using this data, the app can tell you how often your friends check WhatsApp. It can even estimate what time they go to sleep and wake up each day.\r\nEven more impressive (and invasive), Chatwatch can combine WhatsApp data from two of your contacts to make an educated guess if they\u2019ve been talking to each other. Basically, if two of your friends were both online for the same consecutive five minutes in the wee hours of the morning, there\u2019s a decent chance they were messaging each other.\r\nIt\u2019s a creepy new trick that the app\u2019s developers hope will bring more attention to how Facebook handles our data, along with how other companies access and analyze it. It\u2019s also pretty likely that WhatsApp will find a way to block Chatwatch soon. So if you want to\u00a0spy on your friends\u00a0expose Facebook\u2019s privacy issues, you should try it soon.\r\n\u00a0\r\nOne small catch: Chatwatch isn\u2019t free\u2014it\u2019s actually kind of expensive. For $1.99, you get the ability to spy on two of your contacts for a week, so choose carefully. The developers say this money will go towards maintaining the app and funding an\u00a0anti-Trump political non-profit.\r\nChatwatch initially launched on iOS but it was later pulled from the App Store by Apple for unspecified reasons. It\u2019s currently\u00a0available for Android, and the developers are currently working on a web-based version as well.