No-contract carrier Boost Mobile has debuted its first big-screen smartphone, the ZTE Boost Max. Available starting today for $299, the 5.7-inch Boost Max can be had withan annual no-contract $55 Monthly Unlimited plan with Shrinking Payments. Users who make six on-time payments, can shrink their monthly fee by $5, eventually dropping their payments to $40 a month for the carriers unlimited nationwide talk, text and data over Sprints admittedly small LTE network.