Note 7 - Revenue - Remaining Performance Obligations 2 (Details)	Mar. 31, 2022 USD ($)
Revenue, Remaining Performance Obligation, Amount	$ 4,945,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-01
Revenue, Remaining Performance Obligation, Amount	$ 2,011,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Amount	$ 1,698,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Amount	$ 524,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Amount	$ 382,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Amount	$ 330,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Service [Member]
Revenue, Remaining Performance Obligation, Amount	$ 2,008,000
Service [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-01
Revenue, Remaining Performance Obligation, Amount	$ 1,075,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	9 months
Service [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Amount	$ 666,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Service [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Amount	$ 184,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Service [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Amount	$ 83,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Device Revenue [Member]
Revenue, Remaining Performance Obligation, Amount	$ 1,486,000	[1]
Device Revenue [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-01
Revenue, Remaining Performance Obligation, Amount	$ 712,000	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	9 months	[1]
Device Revenue [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Amount	$ 733,000	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year	[1]
Device Revenue [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Amount	$ 41,000	[1]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year	[1]
Exclusivity Fee [Member]
Revenue, Remaining Performance Obligation, Amount	$ 1,262,000
Exclusivity Fee [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-01
Revenue, Remaining Performance Obligation, Amount	$ 214,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	9 months
Exclusivity Fee [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Amount	$ 286,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Exclusivity Fee [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Amount	$ 286,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Exclusivity Fee [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Amount	$ 286,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Exclusivity Fee [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Amount	$ 190,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Product and Service, Other [Member]
Revenue, Remaining Performance Obligation, Amount	$ 189,000
Product and Service, Other [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-01
Revenue, Remaining Performance Obligation, Amount	$ 10,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	9 months
Product and Service, Other [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Amount	$ 13,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Product and Service, Other [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Amount	$ 13,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Product and Service, Other [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Amount	$ 13,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year
Product and Service, Other [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Amount	$ 140,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction (Year)	1 year

[1] Represents the minimum purchase requirements under the distribution agreement the Company signed with its AXP distributor in China.