Fin - just to add, you can mark your jobs as "Remind customer" and they then appear with an orange bell icon next to them throughout the system, including the worksheets on the PC/Mac and mobile app (I think you're already doing this?) With this and SMS set up you get a button top left of the worksheet "Send SMS Reminders" all you have to do is click that, tweak the last message you sent and click "Send" and the message goes out to all customers with mobile numbers and reminders enabled. The orange bell for these customers then goes green and crossed out on the worksheet so you know you've reminded them. The rest you can call or email. Hope that makes sense, feel free to drop me an email or give me a call if you want to discuss further.
PoleKing - didn't used to be possible to develop custom keyboards on iOS but looks like they now support it in iOS 8. OS customisation isn't really my focus to be honest, but I imagine now this is supported in iOS all sorts of custom keyboard apps will start to appear on the App Store. Have you had a hunt round and come up short?