Nature of business, basis of presentation and summary of significant accounting policies (Details Textual) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and Cash Equivalents, at Carrying Value	$ 775	$ 945	$ 486
Accumulated deficit	(123,199)	(119,184)
Amortization of debt discount and deferred financing costs		44
Depreciation expense	10	15
Patent amortization expense	357	365
Impairment of Long-Lived Assets Held-for-use	0	0
Marketing expense	$ 46	$ 15
Estimated remaining weighted average useful lives of patents	P3Y
Minimum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Estimated useful life of related assets, for patents amortization	5 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Estimated useful life of related assets, for patents amortization	17 years