I have my wife's old smart phone to take pics of parts and equipment before disassembly. It doesn't matter if it breaks. It doesn't have cell service but it does have Wi-Fi service. This allows me to download diagrams, search the net for parts, eBay, Craigslist, even post for sale on Craigslist. I can receive email through Wi-Fi. I can back up pics and diagrams to a Micro SD card. I don't have my good phone outside, in the dirt, in the garage. The downside, if I misplace it, I can't call myself to find it!