When we think of the leading smartphone makers, Apple and Samsung are probably the first to come to mind but the top five is usually rounded out by the likes of Xiaomi, Huawei and OPPO and we often forget is that the "Other" category, outside the top five, accounts for well over a third of the global market. And that's where you'll find Vivo, a company that is big in China and India. And their X21 brings an in-display fingerprint scanner to the market.