I've spent some time planning this, and now have the time to try to get it done. The observant will have noticed a new branch ACC just appeared in the github repository.

This is primarily for Tesla Roadster owners, but once we work out how to do charge control in other cars, it will have use for them.

The premise of what I'm thinking is a replacement for the limited charge control in the car, to make an Advanced Charge Control:

We have the concept of a 'charge location'. This is an area (square, because it is easiest) around a GPS location. An area of 200m x 200m, centred on the charge location, should be sufficient for gps inaccuracies. Up to 5 such charge locations can be defined (I'm thinking home, work, and one other).
Once the car enters a charge location, an action can be triggered. At the moment, I'm only thinking of automatic home link activation, but others are possible.
When a car is turned off, while in a charge location, acc is enabled and current charge settings are saved.
When a car is turned on, while in a charge location, acc is disabled and previous charge settings are restored.
Features that acc should support include:

Homelink activation.
Cooldown (cool the car using a sequence of low amperage range mode charges) - this would need a minimum temperature (don't cool down unless ESS temperature is above this), a desired temperature (cool down until the ESS reaches this temperature),and a time limit (stop cooling down if we've been trying for too long).
Charge mode (standard, storage, range, performance).
Charge current limit.
Various charge types, including:

Charge on plug-in
Start charge at specific time
Complete charge by specific time

Desired charge limit (SOC%, ideal miles/kilometers, or full)

In addition to the charge locations, acc should be able to be turned on, one-off, for the current location. This should be done after the car is turned off, before plugging in. It will be effective until the car is turned on again.
It should also be possible to use this one-off acc to override the charge control for the current location. This will be effective until the car is turned on again.
Control, and status, is possible by SMS commands.
Control is also possible by a new tab added to the apps. I'm going to do iPhone first, with the existing charge control moved to a new "Charge" tab.

I'm not sure how to do the 'specific time'. This could be simple-to-ludicrously-complex. My inclination is to just put a day-of-week filter on each charge location - with acc only being enabled if the day matches. More than one location could be created for each physical gps location, with different day matches, to control how that would behave.

Changes to be made include:

Move the roadster digital speedo experimental feature to a fully supported features, and give it a permanent feature storage number.
Assign five new permanent parameters, one each for five charge locations (home, work, other, or whatever they want to be known as - we just call them #1, #2, #3, #4 and #5).
The parameter storage for these new locations includes the charging preferences for each location.
We would also need a parameter for time zone.
Add a new module called "acc".
If "acc" detects we are at a known charge location, it will take over the charge control from the car.
The "acc" will also support commands for the current location, and will be able to take over charge control from now until the car is next driven.

Please let me have your comments / suggestions. I'll handle the coding, but I'll need lots of help testing.