Samsung's Gear S smartwatch is unique for its ability to make calls and get online without pairing to a nearby phone, but that luxury may not come cheap.

According to a leaked Sprint memo published by Phandroid, the carrier intends to charge $10 per month for Gear S service. Subscribers can either tap into their existing Family Share plans, which include unlimited talk and text, or buy a standalone plan with 1000 minutes, 1000 messages and 100MB of data. Either way, the monthly cost is the same.

Samsung announced the Gear S in late August, but the company hasn't disclosed pricing or release dates. While Samsung has said the watch will be available through all four major wireless carriers, none of them have officially revealed how voice, text and data plans will work for this new device type.

AT&T has said that users will need to have their phones turned on and connected to the network, even when the watch isn't nearby, but there's no mention of that in the leaked Sprint memo. The memo does note that users won't be charged against their plan limits when the watch is paired to a smartphone over Bluetooth.

Why this matters: Smartwatches have already proven to be a hard sell for mainstream users, even without an additional monthly fee on top. While a lack of standalone functionality could be the thing that's keeping people away, asking users to pay for that feature is a big gamble. It could pay off handsomely for carriers like Sprint, but it could just as easily doom Samsung's next smartwatch from day one.