Quick update.
Behind the scenes we have been developing a CRM for this industry. Most CRM's in the automotive industry are focused on having a shop. The few that do cater to the mobile side are usually either half-baked or not much better than your calendar app and Google Maps.
Initial focus is just mobile oil change, but will add mobile mechanic features as well.
I am looking for a handful of beta testers. If you're interested, please DM your email and maybe a quick note. I'm only looking for 5-10 folks. If you're active in the beta testing process I'll be sure to take care of you when the app goes live with a generous discount.