You might be able to sell gift cards for miles in the future in CardCash. Below is what I see from one of their pages. Looks like they are working on more channels (id 6 - 9 below) to pay you.
{
"id": 1,
"option_title": "PayPal Payment",
"status": 4,
"trade": 0,
"description": "",
"opt_Id": "paypal_payment",
"opt_Name": "payment_type",
"discount_rate": 0,
"zen_type": 1,
"zen_pay_type": 1
},
{
"id": 2,
"option_title": "ACH Deposit",
"status": 4,
"trade": 0,
"description": "",
"opt_Id": "ach_deposit",
"opt_Name": "payment_type",
"discount_rate": 0,
"zen_type": 1,
"zen_pay_type": 2
},
{
"id": 3,
"option_title": "Mailed Check",
"status": 1,
"trade": 0,
"description": "",
"opt_Id": "mail_check",
"opt_Name": "payment_type",
"discount_rate": 0,
"zen_type": 1,
"zen_pay_type": 3
},
{
"id": 4,
"option_title": "Trade & get paid more",
"status": 4,
"trade": 0,
"description": "",
"opt_Id": "trade_more",
"opt_Name": "payment_type",
"discount_rate": 0,
"zen_type": 1,
"zen_pay_type": 0
},
{
"id": 5,
"option_title": "Amazon gift card",
"status": 0,
"trade": 1,
"description": "Coming soon!",
"opt_Id": "trade_amazon",
"opt_Name": "tradeType",
"discount_rate": 4,
"zen_type": 3,
"zen_pay_type": 0
},
{
"id": 6,
**"option_title": "CVS cards",**
"status": 0,
"trade": 1,
"description": "Coming soon!",
"opt_Id": "trade_cvs",
"opt_Name": "tradeType",
"discount_rate": 5,
"zen_type": 6,
"zen_pay_type": 0
},
{
"id": 7,
**"option_title": "United air miles",**
"status": 0,
"trade": 1,
"description": "Coming soon!",
"opt_Id": "trade_united",
"opt_Name": "tradeType",
"discount_rate": 6,
"zen_type": 7,
"zen_pay_type": 0
},
{
"id": 8,
**"option_title": "Walmart",**
"status": 3,
"trade": 1,
"description": "",
"opt_Id": "trade_walmart",
"opt_Name": "tradeType",
"discount_rate": 6,
"zen_type": 8,
"zen_pay_type": 0
},
{
"id": 9,
**"option_title": "CardCash Gift Card ",**
"status": 0,
"trade": 1,
"description": "Coming soon!",
"opt_Id": "trade_cardcash",
"opt_Name": "tradeType",
"discount_rate": 0,
"zen_type": 9,
"zen_pay_type": 0
}