Square is seeing more competition from established players in the payments market.
The latest challenger is from VeriFone who has launched a similar mobile platform named SAIL.
SAIL by VeriFone features a mobile attachment and lets you accept credit card payments using your iPhone or Android phone/tablet.
The card reader is available for free. Charges:
1.95% on each transaction if you pay a USD 10 subscription per month
2.7% on each transaction with no subscription