PDAs provide low cost, portable and mobile platforms for HMI implementations. Companies such as Symbol, Intermec Technologies, Psion Teklogix and Unitech provide PDAs that trade off some compactness for ruggedness while incorporating additional functionality such as barcode scanning. There are even explosion proof and intrinsically safe versions of PDAs available (Ecom Instruments). Some manufacturers provide built-in RFID reader. Several manufacturers provide built-in WiFi.