As far as I know, there is no such ETF as of today. However, the recent spike is likely to spark even more the interest of the best ETFs issuers out there (Vanguard, iShares...).
It is not complex at all, actually it would be very cheap compared to setting up traditional ETFs. The fund would just have to keep bitcoins in an offline wallet held in a secure vault somewhere, just as if it were gold or any other precious metal.
Now given the current market volatility of bitcoin vs. other currencies, it could be considered as too dangerous marketing-wise to be offered to retail investors (even if it would be a less complex product than for example leveraged ETFs).
More importantly, at this stage the key preventing factor could be the low liquidity available on the various exchanges (Mt. Gox and others): bitcoins are nowhere as liquid as other currencies, thus transaction costs in terms of market impact could be astonishingly high and significantly affect the fund's performance.
That being said, I do believe this will eventually happen, sooner rather than later, either with bitcoin or with an alternate equivalent currency. Then, you can also expect future and option markets to flourish (for hedging purposes).