I only need a few requirements:

1. Ability to power laptop and cell phone when the car is off.
2. This power supply should be rechargeable from within the car.
3. The car should always be able to start on its own.

So I've got these ideas:

1. Battery Brain (BatteryBrain) + regular car batttery: easy to use, grants power from main battery to power stuff, main battery charged by alternator, prevents main battery from discharging too much. Downside is that a regular battery can still be killed with this continual discharge/recharge cycling.

2. Battery Brain + deep cycle automotive battery (which one?): all benefits of above and battery should not be able to be killed as quickly, but finding a deep cycle that can jump a car and fit in the Honda Fit will be difficult if impossible? Available energy capacity less than a regular car battery.

3. Regular battery + battery isolator + deep cycle: more involved to set up, grants power from deep cycle battery to power stuff, main and deep cycle battery charged by alternator. Downside is that setup is more involved and I need to continually carry a deep cycle battery somewhere in the car with me.

4. Buy a high quality battery with a good warranty and just keep on swapping it out when it dies.

5. A portable battery pack with its own inverter and chargeable from the lighter socket. Downsides are that I have to carry an extra battery with me and there's no telling if the battery pack uses a deep cycle or a regular one.

What other deep cycle automotive batteries are available for the 2010 Honda Fit other than the Yellow Tops?