99taxi is not a very new app, but it's worth mentioning they're owned by China's Didi Chuxing so it is a reputable provider. You can use your facebook profile and link to your Paypal, so prob works well for foreigners. You have the option of ordering regular yellow taxis (discounted rate) or a 99POP which is basically the same cars as UberX but even cheaper (if you know how low UberX prices are in Brazil then perhaps like me you'll feel a little embarrassed of using 99POP as it almost feels like exploitation!).

Anyway, good tip.