In this paper, a sub-meter real-time positioning service for smartphones is presented. Known as FLAMINGO, the service has been in operation since early 2020. Relying only on GNSS currently, FLAMINGO can deliver 50 cm or better accuracies to consumer devices such as smartphones or IOT. The Android smartphone is considered in this paper, harnessing the availability of Google Android Raw GNSS Measurements, which have been made available to Huawei, Samsung, Xiaomi, and other Android handsets since 2016. Since the release of these measurements, the GNSS community has made significant progress to improving the performance of GNSS in the smartphone. FLAMINGO harnesses the best-of techniques from PPP and RTK, modifying, and tweaking the configuration and pre-processing to improve the raw GNSS measurements from an Android device. These measurements are prone to high errors due to the poor quality of the mobile chipset receiver. Given these drawbacks, sub-meter positioning is achieved. This is demonstrated through static baseline tests, and suburban and urban kinematic trials. These tests have been repeated to ensure the user always experiences an accurate and reliable service. It is important to consider that all tests have been performed live, where a test app was developed to replicate the user experience of FLAMINGO.