Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities:
Net loss	$ (2,232)	$ (3,706)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	234	426
Amortization of debt discounts and financing issuance costs	190
Change in fair value of warrant liability	(708)
Provision for doubtful accounts and other adjustments to accounts receivable	74
Provision for excess and obsolete inventory		3
Loss on disposal of fixed assets		2
Non-cash compensation related to stock options, ESPP and restricted stock	446	361
Change in operating accounts:
Accounts receivable	183	2,686
Inventories	(1)	9
Prepaid expenses and other assets	209	(208)
Accounts payable and accrued liabilities	(695)	17
Deferred revenue	586	667
Net cash provided by (used in) operating activities	(1,714)	257
Investing activities:
Capital expenditures	(13)	(86)
Proceeds from the sale of short-term investments		2,401
Net cash provided by (used in) investing activities	(13)	2,315
Financing activities:
Cash received from stock sale for employee stock purchase plan	2	7
Cash received from related-party notes payable	2,000
Net cash provided by financing activities	2,002	7
Net increase in cash and cash equivalents	275	2,579
Cash and cash equivalents, beginning of period	2,229	8,819
Cash and cash equivalents, end of period	2,504	11,398
Supplemental disclosures of cash flow information:
Cash paid for income taxes	2	$ 21
Cash paid for interest expense	$ 120