Note 8 - Segment Reporting (Details) - Total Revenues by Products and Services (USD $)
In Thousands, unless otherwise specified
3 Months Ended 9 Months Ended
Jan. 31, 2014
Jan. 31, 2013
Jan. 31, 2014
Jan. 31, 2013
Revenue from External Customer [Line Items]        
Total sales by products and services $ 7,683 $ 7,458 $ 21,787 $ 17,853
Original Equipment Manufactures [Member]
       
Revenue from External Customer [Line Items]        
Total sales by products and services 2,984 4,382 10,757 9,800
Remote Monitoring Solutions [Member]
       
Revenue from External Customer [Line Items]        
Total sales by products and services 3,926 1,357 8,260 4,208
Industrial Data Communications [Member]
       
Revenue from External Customer [Line Items]        
Total sales by products and services 333 113 829 624
Mobile Data Acquisition [Member]
       
Revenue from External Customer [Line Items]        
Total sales by products and services 265 1,484 1,439 2,765
OEM Related Services [Member]
       
Revenue from External Customer [Line Items]        
Total sales by products and services 48 42 173 168
Proprietary Product Related Services [Member]
       
Revenue from External Customer [Line Items]        
Total sales by products and services $ 127 $ 80 $ 329 $ 287