Accessories used to be limited to cases, spare batteries, and the like, but now it can mean smart watches and (overpriced) headphones that cost almost as much as your phone. That's why T-Mobile wants to make it easier to blow cash on them. According to TmoNews, T-Mobile will begin offering Equipment Installment Plans (EIP) for accessories on July 20th.
Right now, EIPs are only available for phones. This is actually the only way to buy a phone on T-Mobile if you don't want to pay full price up front – there are no contracts anymore. All you do is pay a little bit of the cost each month until it's paid off. It's basically an interest-free loan, and you'll be able to tack on a smart watch soon.
T-Mobile offers devices like the $300 Samsung Gear 2, which would work out to $12.50 added to your bill for two years. A set of $200 Beats Solo headphones would be $8.33 per month for 24 months. The details are not clear yet, though. It's possible T-Mobile will require a shorter term to pay off an accessory, for example. Whatever happens, get ready for Tmo to start pushing more phone/watch bundles.