Yesterday, the largest component of the S&P 500 and Nasdaq-100, Apple (NasdaqGS: AAPL), rallied more than 2.5% and is up an additional 0.75% in the early going this morning (trading at approximately $615).

This is notable because it was only last Wednesday where the stock plunged below the $600 level but quickly found support around its 50 day moving average as well as longer term technical trend-line.

While the rally in the stock over the past two days can at least be partially attributed to rumors present yesterday that the stock may split and/or pay a dividend, market observers have to watch AAPL closely simply because of its lofty, and growing weight in prominent market cap weighted indices including the SPX and NDX (at 4.54% and 17.98% respectively). [How an Apple Stock Split Would Impact ETFs]

It is also fair to say that as AAPL goes, the entire Tech sector goes as AAPL has a 19.63% weighting in XLK (SPDR Technology Sector) for instance, with the next highest weighted stock, IBM, coming in at only 8.14%.

ETFs that have significant exposure to AAPL that may be very active in the short term and are certainly worth monitoring include, IYW (iShares DJ U.S. Technology, where AAPL has a 23.11% weighting), FTQ (FocusShares Morningstar Technology, with a 21.62% weighting to AAPL), VGT (Vanguard Info Technology, with a 18.00% weighting to AAPL), and IXN (iShares S&P Global Technology, with a 17.93% tilt to AAPL).

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