Loyal3 sells 38 companies currently in the S&P 500 (FOXA, AMZN, AAPL, BRK.B, BBY, KO, DISCA, DIS, DPS, EA, FB, FTR, GPS, GOOG, HAS, HSY, INTC, K, KSS, LB, M, MAT, MCD, MSFT, MDLZ, MNST, NKE, PVH, PEP, RL, SBUX, TGT, TWX, VFC, VIAB, WMT, YUM, and YHOO). On first glance, this seems like a relatively diverse group of retailers, manufacturers, restaurants, technology companies, media companies, and a few others.
The S&P 500 index is weighted by market cap. I made a spreadsheet with these stocks weighted by market cap (as of 1/1/2013). Buying on that date and holding throughout 2013 would produce a 27% price increase by 1/1/2014, plus dividends. SPY returned 32.13% (including dividends) over that time period. That's pretty comparable.
One word of warning about this approach is that market-cap (either on 1/1/2013 or today) would have caused you to invest half your money in just five companies: Apple, Google, Wal-Mart, Microsoft, and Berkshire Hathaway. This effect (large percentages of your investment going to the largest few companies) is present in all weighted indexes, but it's exacerbated by the fact that your "index" here only includes 38 companies.