Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenues	$ 6,945	$ 5,862	$ 12,408	$ 11,438
Cost of revenues	1,116	1,285	2,425	2,568
Gross profit	5,829	4,577	9,983	8,870
Operating expenses:
Selling and marketing	1,447	1,461	3,177	3,254
Research and development	2,195	2,174	4,450	4,671
General and administrative	2,061	2,239	4,251	4,428
Restructuring expense	52	322	52	714
Total operating expenses	5,755	6,196	11,930	13,067
Operating income (loss)	74	(1,619)	(1,947)	(4,197)
Other expense:
Interest expense, net	(143)	(329)	(314)	(613)
Change in fair value of warrant liability	(2,085)		(2,224)
Other income (expense)	(10)	1	(50)	(9)
Loss before provision for income taxes	(2,164)	(1,947)	(4,535)	(4,819)
Provision for income tax expense	13	5	23	13
Net loss	$ (2,177)	$ (1,952)	$ (4,558)	$ (4,832)
Net loss per share:
Basic and diluted	$ (0.11)	$ (0.15)	$ (0.26)	$ (0.38)
Weighted average shares outstanding:
Basic and diluted	21,888	13,179	18,612	12,674
Preferred dividends per share	$ 50.38		$ 71.16