This table compares the openaltimeter's features with other DLG electronics that I know about. I've tried to make it as fair as possible, but given that I designed the openaltimeter, you should probably take it with a pinch of salt! It was made in November 2010. If it's now after that, things might have moved on :-)

openaltimeter How-High RAM3 ZLog EagleTree altimeter LoLo5 PLD-BAC-LMA
LiPo regulator Yes N/A N/A N/A N/A N/A Yes
Low-voltage alarm Yes N/A N/A N/A N/A N/A Yes
Lost-model alarm Yes-ish (*5) N/A N/A N/A N/A N/A Yes
Logging altimeter Yes No (*1) Yes Yes No Yes N/A
In-situ altitude readout (*2) Yes Yes No No No No N/A
Open-source firmware Yes No No No No No No
Open-source plotting app Yes N/A No No No No N/A
Weight 5.3g (*3) 2.2g 2.25g 8g 4g 4g 5.5g
Memory (samples) 262144 90 64800 16378 ? 432000 N/A
Size 31 x 16mm 20 x 15mm 20 x 16mm 40 x 23mm 28 x 16mm 23 x 15mm 19 x 12.5mm
Current consumption 4.5mA 1.2mA 5mA 13mA ? 8mA ?
Price (*4) $72 $39.90 $79 ? $38 $173 $31.50