Cryptocurrency arbitrage opportunity app
arbitrage.expert
arbitrage.expert
What is also not displayed is the logistical possibility of executing some of these trades due to hidden KYC limitations.
For example, it currently shows a 2.02% spread between cex.io and GDAX for BTC/USD. Unfortunately, CEX.io does not provide an option to withdraw using fiat for United States citizens; the only way for United States citizens to get money out of CEX.io is buying crypto and transferring the crypto. This means that the "spread" turns out to be a premium for liquidity; if you bought 1 BTC on GDAX ($7880) and transferred it to CEX to cash out @ $8049 for a profit of $169, you would find that instead you'd have to buy some other similarly inflated crypto on CEX to bring your $8049 out.
This technically means that when CEX.io is the high market and GDAX is the low market, the trade would only work if you could naked short sell on CEX.io; then you could immediately get $8049 for an IOU for 1 BTC which you could satisfy by sending yourself 1 BTC you bought on GDAX. This might be possible using the margin trading facilities on CEX.IO?
Insidiously, CEX.IO accepts USD deposits but not withdrawals, so I found out about this the hard way.