Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (1,140)	$ (2,473)	$ (1,642)	$ (1,165)	$ (4,340)	$ (541)	$ (5,255)	$ (6,046)
Adjustments to reconcile net loss to net cash used in operating activities:
Other income - employee retention tax credit	(862)			0			(862)	0
Gain on forgiveness of PPP loan	0			0			(801)	0
Depreciation	43			48			143	140
Stock-based compensation	39			35			387	96
Change in fair value of warrant liabilities	0			(153)			0	2,274
Provision for doubtful accounts receivable	2			(9)			10	(21)
Provision for slow-moving and obsolete inventories	(70)			90			(9)	(229)
Provision for warranties	1			14			13	34
Amortization of loan discounts and origination fees	61			145			158	221
Changes in operating assets and liabilities (sources / (uses) of cash):
Accounts receivable	(500)			(901)			390	(1,070)
Inventories	444			551			(2,105)	1,138
Short-term deposits	(62)			(197)			87	(412)
Prepaid and other assets	(91)			(76)			(119)	(59)
Accounts payable	(164)			534			(82)	1,811
Accrued and other liabilities	53			160			(305)	453
Deferred revenue	(69)			44			(70)	87
Total adjustments	(1,175)			285			(3,165)	4,463
Net cash used in operating activities	(2,315)			(880)			(8,420)	(1,583)
Cash flows from investing activities:
Acquisitions of property and equipment	(100)			(53)			(311)	(171)
Net cash used in investing activities	(100)			(53)			(311)	(171)
Cash flows from financing activities (sources / (uses) of cash):
Proceeds from the issuance of common stock and warrants	0			(1)			5,000	2,749
Proceeds from the exercise of warrants	0			625			527	676
Offering costs paid on the issuance of common stock and warrants	(1)			0			(470)	(474)	$ (510)
Proceeds from PPP loan	0			0			0	795
Principal payments under finance lease obligations	(1)			(1)			(3)	(3)
Proceeds from exercise of stock options and employee stock purchase plan purchases	0			0			59	30
Common stock withheld in lieu of income tax withholding on vesting of restricted stock units	1			0			(1)	(3)
Proceeds from the Streeterville note	0			0			1,515	0
Payments on the Iliad note	0			(450)			0	(976)
Deferred financing costs	0			(320)			(30)	(320)
Net payments on credit line borrowings - AFS	0			(1,296)			0	(719)
Net proceeds from the credit line borrowings - Credit Facilities	1,128			2,223			337	2,223
Net cash provided by financing activities	1,127			780			6,934	3,978
Net (decrease) increase in cash and restricted cash	(1,288)			(153)			(1,797)	2,224
Cash and restricted cash, beginning of period	1,669		$ 2,178	3,069		$ 692	2,178	692	692
Cash and restricted cash, end of period	381	1,669		2,916	3,069		381	2,916	2,178
Classification of cash and restricted cash:
Cash	381			2,574			381	2,574	1,836
Restricted cash held in other assets	0			342			0	342	300
Cash and restricted cash	$ 381	$ 1,669		$ 2,916	$ 3,069		$ 381	$ 2,916	$ 2,178