Harry Ferreira, head of small business at BNZ, said the device tackled one of the big pain points for SMEs - how to manage cash flow while waiting for payments.
"This technology allows businesses to take payments on the spot and funds will be in their account as early as the next business day," Ferreira said.
"We believe this will transform the landscape of payments for small and medium businesses in New Zealand."
SMEs were increasingly looking to "un-tether" from their offices.
The likes of plumbers, electricians or vendors at a farmer's market could now easily and cheaply offer an electronic payment service to customers, he said.
PayClip has been developed by Mint Wireless, a listed Australian company which also has offices in London and Singapore.
BNZ said it was the first New Zealand bank to offer PayClip, which will be available to business customers from next month.
Those who sign up will pay a flat fee of $10 per month, plus a 3.25 per cent fee from every transaction.
Ferreira said many businesses were unhappy with the current price of eftpos terminals, which cost between $65 and $100 a month.
"It will be significantly cheaper for retailers to use this, and also guys on the road as well."
The first phase of the roll-out requires customers to write their signature on the mobile screen to authorise payments. Later phases will enable pin and contactless tap-and-go payments.
When the customer makes their payment, they can choose to receive a receipt by email or text.
Ferreira said he hoped to have "tens of thousands" of businesses using the technology within 12 months.
Last week, Vodafone announced that it had teamed up with Visa and BNZ for the trial of its new SmartPass phone app.
The digital wallet application means users can simply place their phone on a tap-and-go eftpos terminal, using near-field communication technology (NFC) to make transactions.