Historically, currency trading had been done through futures accounts, making this the realm of sophisicated traders and currency professionals. But with the advent of exchange-traded funds that replicate movements in global currencies, even the novice can now participate.

I'd caution, that despite the ease with which one can now trade currency-based ETFs, understanding the inter-relationship of currencies and forecasting moves in individual currencies remain complex topics.

Two advisors with a long-standing expertise in this area are Mary Anne and Pamela Aden -- who offer their outlook for the US dollar, and their top picks among currency ETFs.

They explain, "Interest rates are an important influence in the currency markets." In their newsletter, The Aden Forecast, they continue, "Currently, U.S. interest rates are higher than the euro rate. But euro interest rates are rising and they're at a five year high, while the rise in U.S. rates is slowing down and the next direction for U.S. interest rates is likely down. That now makes the dollar unattractive and the euro more desirable.

In other words, the sisters explain, "The dollar's interest rate advantage has diminished and that's very bearish for the dollar."

This is serious situation, they note, especially since many countries are diversifying out of their dollar holdings. As an example, they cite China. The sisters observe, "China has formed a new agency that will diversify their massive trillion dollar reserves into other currencies."

In addition, they note, "As the dollar heads lower, other countries could speed up their diversification plans as well, which would help fuel the dollar's decline and boost the euro as demand for the euro grows."

If as they suggest, the US dollar is headed lower, then select foreign currencies will rally. To play this expected trend, the sister recommend that investors hold positions in foreign currencies through exchange-traded funds.

Their recommended positions are Australian Dollar Trust (NYSE: FXA), the Euro Currency Trust (NYSE: FXE), the British Pound Sterling Trust (NYSE: FXB), and the Swiss Franc Trust (NYSE: FXF).

For more stock picks from the leading financial newsletter advisors, visit Steven Halpern's free daily website, TheStockAdvisors.com.