I use an app called Business Calendar (they have both a free and a pro version), and you can create multiple reminders within it, with as short a reminder as 1 minute before said appointment, and go out as far as 4 weeks. If that's not to your liking, you might be better off using the desktop version of Google Calendar, as you can adjust any of the reminders to go at any point you desire. I can't think of any calendars (offhand anyway) that notify the instant that they're created.

 

Does each tech have his or her own calendar? Maybe you could create one master calendar that holds all of the appointments, and use the invitation feature to send out an email to the individual tech for whom you're booking it. Said tech could then click on the link to accept the appointment into their respective calendar, and he or she could add their own reminders from there. The only kink to this would be if they don't have their Google accounts syncing, which is what allows the gmail to operate a push account. If that's up and running on each Android phone, they would get notifications the instant the invite email hits their devices.