Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Statement of Cash Flows [Abstract]
Net loss	$ (13,178)	$ (22,693)
Adjustments to reconcile net loss to net cash used in operations:
Depreciation	923	1,445
Amortization of intangible assets	158	184
Impairment of intangible assets	277	284
Gain on disposal of property and equipment	(35)	(79)
Realizeld loss on sale of short-term investments	0	32
Non-cash stock-based compensation expense	1,606	2,269
Change in warrant liability	(1,801)	0
Realized gain on warrant exchange	(99)	0
Inventory write-downs	303	1,094
Non-cash deferred rent	(31)	(118)
Change in:
Accounts receivable, net	1,091	(652)
Costs and estimated earnings in excess of billings on uncompleted contracts	12	58
Inventory	145	2,663
Other current assets	868	(419)
Other assets	4	12
Accounts payable	(1,486)	(4,077)
Accrued liabilities	(1,387)	(1,175)
Deferred revenue	(609)	609
Billings in excess of costs and estimated earnings on uncompleted contracts	582	(58)
Net cash used in operating activities	(12,657)	(20,621)
Cash flows from investing activities
Sales of investment securities	0	11
Decrease in restricted cash	1	350
Proceeds on sale of property and equipment	35	80
Purchases of property and equipment	(376)	(533)
Net cash used in investing activities	(340)	(92)
Cash flows from financing activities
Principal payments under capital leases and long-term debt	(120)	(136)
Net proceeds from issuance of common stock and warrants	11,642	14,624
Net cash provided by financing activities	11,522	14,488
Net decrease in cash and cash equivalents	(1,475)	(6,225)
Cash and cash equivalents, at beginning of period	6,850	13,075
Cash and cash equivalents, at end of period	5,375	6,850
Supplemental disclosure of cash flow information
Cash paid for interest	12	30
Supplemental schedule of non-cash investing and financing activities
Other non-cash additions to property and equipment	407	0
Issuance of common stock for exchange of warrants	$ 536	$ 0