This is the parts list for 3G SMS controlled Hot Water Heater Detailed at www.forward.com.au/pfod/pfodSMS/SMS_HotWater.html (approximate prices as at 25th June 2018, shipping extra) Arduino Mega 2560 -- https://www.sparkfun.com/products/11061 (~US$46) or SainSmart MEGA2560 R3 (~US$24) Adafruit FONA 3G SIM5320 breakout board -- (Note the optional 'free Ting Sim' is 2G only) https://www.adafruit.com/product/2691 European frequencies (~US80) -- I used this one on the Australian Optus network OR https://www.adafruit.com/product/2687 American frequencies (~US80) Lithium Ion Polymer Battery - 3.7v 1200mAh -- https://www.adafruit.com/product/258 (~US10) USB power supply 1A -- https://www.sparkfun.com/products/11456 (~US4) OR https://www.adafruit.com/product/501 (~US$6) Solid State Relay with heat sink -- FOTEK SSR-40 DA amazon (~US$14) also from numerous other sources look for one with a cover ( and Heat Sink Compound, if not included with Solid State Relay -- https://www.sparkfun.com/products/9599 (~US$2) ) OR for load less then 10A Optically isolated 240V/110V AC 10A relay module -- see https://www.forward.com.au/pfod/HomeAutomation/OnOffAddRelay/index.html#single5V pfodDesigner -- https://play.google.com/store/apps/details?id=au.com.forward.pfodDesigner (free) pfodApp -- https://play.google.com/store/apps/details?id=au.com.forward.pfodApp (~US$10) Polycarbonate Mounting box and perspex mounting boards and screws e.g. Jaycar HB-6248 (171mm x 121mm x 55mm) https://www.jaycar.com.au/sealed-polycarbonate-enclosures-171-x-121-x-55-clear-lid/p/HB6248 4mm screws for internal base place, 3mm and 2.5mm nylon screws and spacers for mounting NOTE The Adafruit FONA needs 2.5mm screws -- https://www.adafruit.com/product/3299 or https://www.adafruit.com/product/3658 Jaycar has 3mm screws and hex tapped spacers and 4mm metal screws. The 4mm screws need to be cut down to length.