Identifying　the　object　that　attracts　human　visual　attention　is　an　essential　function　for　automatic　services　in　smart　environments.　However,　existing　solutions　can　compute　the　gaze　direction　without　providing　the　distance　to　the　target.　In　addition,　most　of　them　rely　on　special　devices　or　infrastructure　support.　This　paper　explores　the　possibility　of　using　a　smartphone　to　detect　the　visual　attention　of　a　user.　By　applying　the　proposed　VADS　system,　acquiring　the　location　of　the　intended　object　only　requires　one　simple　action:　gazing　at　the　intended　object　and　holding　up　the　smartphone　so　that　the　object　as　well　as　user＇s　face　can　be　simultaneously　captured　by　the　front　and　rear　cameras.　We　extend　the　current　advances　of　computer　vision　to　develop　efficient　algorithms　to　obtain　the　distance　between　the　camera　and　user,　the　user＇s　gaze　direction,　and　the　object＇s　direction　from　camera.　The　object＇s　location　can　then　be　computed　by　solving　a　trigonometric　problem.　VADS　has　been　prototyped　on　commercial　off-the-shelf　(COTS)　devices.　Extensive　evaluation　results　show　that　VADS　achieves　low　error　(about　1.5.　in　angle　and　0.15m　in　distance　for　objects　within　12m)　as　well　as　short　latency.　We　believe　that　VADS　enables　a　large　variety　of　applications　in　smart　environments.