This study aims to (i) identify patterns of sociophonetic variation in Taiwan Mandarin, and (ii) evaluate smartphone technologies as a tool for crowdsourcing sociophonetic data. Specifically, this study examines both phonological variables found in prior literature to be highly salient (deretroflexion, labiovelar glide deletion), and variables that are less likely to index social properties (merging of final /n, ŋ/, changes to Tones 2 and 3). Unlike past studies which have primarily relied on smaller sample sizes, this study utilizes a smartphone application to crowdsource audio recordings across Taiwan; subsequent Rbrul analysis of 292 recordings revealed robust patterns of sociolinguistic variation. Deretroflexion correlates strongly with gender and age, while glide deletion correlates with gender. Nasal final merging and tonal change exhibit less socio-indexical variation, but provide evidence of potential change in progress. These findings suggest that smartphone-based crowdsourcing can complement traditional sociolinguistic fieldwork, and reveal new knowledge about large-scale variation.