This script follows the Tier et Tout betting strategy explained here: http://www.roulette30.com/2010/04/tier-et-tout.html

A bet amount (preferably divisible by 3) is used, the first third is bet at 2x payout. If it wins, the profit from that win is divided by three, and is added onto the original base bet. This goes on until the profit target or profit limit is reached. If the profit target is reached, the bot resets back to the base bet. If the profit limit is reached, the bot outputs the profit won, resets bet to base bet, and stops automatically. If there is a loss, the last two thirds of the current bet amount is bet, switching the roll from high to low or from low to high. The bot is smart, during a loss streak, it only bets the first third until a win occurs.

Here is an example:

Starting Bet Amount: 9

Bet  Result  Profit  Balance
3     Win      +3      12
4     Win      +7      16 (16/3 = 5.33, bot keeps 1 unit)
5     Loss     +2      11
10    Win      +12     21
7     Win      +19     28

This is a favorable session. Risking 9 units gave 28.

Because the bot wins a lot of units on a long streak, a high profit target or limit will allow safe increase in balance.