yep, lots of people are doing it. so much so that by the time your bot has noticed a promised gap in the spread, 500 other people have already hit it.
if you really want some simple tradin advice:
1: buy low
2: sell high
3: never sell at a loss
follow those rules and you'll always profit. the only limit on that is the waiting time of the profits.
as for:
The confirmation process for both bitcoin and litecoin are way too lengthy for high frequency to happen.
once you made your deposit into an exchange, trading within the exchange is near on instantanious. but if you are talking about trading between the price differences of different exchanges. that is called arbitrage, and even with fiat. there is a big delay.
EG swapping dollar from one bank account to another takes 3 days in the US