Garmin ( GRMN) is another stock that's showing traders a bullish buying opportunity this week. For Garmin, the setup in play is a double bottom, a reversal pattern that's formed when a stock makes two big swing lows that bottom out at approximately the same level. The buy signal becomes the breakout above the peak that connects those twin troughs. For Garmin, that breakout level comes in at $43. A move above that price is our buy signal in this $8 billion GPS maker... Garmin could get an added shot in the arm from its inclusion in the S&P 500 index -- the firm took its spot in the big index after the close on December 11. Between forced buying from index funds and the psychological effects for retail investors, GRMN could well see its momentum continue for a while.