Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (9,452)	$ (13,064)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	94	59
Loss on disposition of property and equipment	1	0
Stock-based compensation expense	560	746
Change in fair value of common stock warrants	(1,323)	1,177
Inducement charge for Series C warrants	0	3,050
Non-cash expense of issuing shares to Aspire Capital	0	183
Change in fair value of contingent consideration	35	0
Change in operating assets and liabilities:
Accounts receivable	19	(94)
Inventory	(152)	(267)
Prepaid expenses and other assets	(50)	27
Other long-term assets	(50)	0
Accounts payable	175	542
Accrued compensation and other current liabilities	(719)	720
Other long-term liabilities	52	0
Net cash used in operating activities	(10,810)	(6,921)
Cash flows from investing activities:
Cash paid for purchase of assets of NeoForce Group, Inc.	0	(1,000)
Increase in restricted cash	0	(91)
Cash paid for patent acquisition	0	(150)
Purchase of property and equipment	(39)	(48)
Net cash used in investing activities	(39)	(1,289)
Cash flows from financing activities:
Initial public offering costs paid	0	(530)
Proceeds from issuance of common stock		1,434
Proceeds from exercise of common stock options	70	294
Repayment of credit line	0	(102)
Net cash provided by financing activities	10,769	4,973
Net decrease in cash and cash equivalents	(80)	(3,237)
Cash and cash equivalents, beginning of period	5,495	7,957
Cash and cash equivalents, end of period	5,415	4,720
Supplemental disclosures of noncash investing and financing information
Conversion of Series A preferred to common stock	2,220	0
Patent costs included in Accrued liabilities	0	300
Stock issuable in consideration for Patent purchase	0	112
Reduction in initial public offering costs payable	0	45
Cashless exercise of 2010/2012 warrants	0	13
Series B transaction costs in accounts payable	52	0
Fixed asset purchases in accounts payable	11	0
Series A Convertible Preferred Stock [Member]
Cash flows from financing activities:
Proceeds from sale of preferred convertible stock	5,071	0
Initial public offering costs paid	(71)	0
Series B Convertible Preferred Stock [Member]
Cash flows from financing activities:
Proceeds from sale of preferred convertible stock	13,479	0
Series A Warrant Liability [Member]
Cash flows from financing activities:
Redemption of Series A preferred convertible stock in conjunction with issuance of Series B Convertible Preferred	(7,780)	0
Proceeds upon exercise of warrants	0	156
Series A Warrant Liability [Member] | Cash Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	0	42
Private Placement Series B Warrants [Member]
Cash flows from financing activities:
Proceeds upon exercise of warrants	0	3,832
Tender Offer Series B Warrants [Member]
Cash flows from financing activities:
Proceeds upon exercise of warrants		6
Series B Warrant Liability [Member]
Cash flows from financing activities:
Proceeds upon exercise of warrants	0	189
Series B warrant transaction costs paid	0	(306)
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	0	3
Series B Warrant Liability [Member] | Cash Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	0	6,747
Series B Warrant Liability [Member] | Cash Less Exercise [Member]
Supplemental disclosures of noncash investing and financing information
De-recognition warrant liability	$ 593	$ 9,475