Have you thought about the Garmin Forerunner 210. It does average or current pace, lap times (automatic or manual) and it can be programmed for intervals. It is very simple to use and the display is quite clear. The only downside to it is the charging/sync connection they have decided to use.
I have had to do numerous bleep tests for jobs and have one coming up in a couple of weeks, however I am training for a half marathon so I am not doing anything specific for this test.
I do agree that you need to up your running for a few sessions to 30+ min, at 1% incline, at a steady conversational pace.
I would also try and do a run where you do increase the speed as time goes on, as suggested by Happy as this is the nearest you are going to get to simulate the bleep test on a treadmill.
If you can include a few shuttle runs/bleep tests in the training then all the better as it will get you used to the stop/start, turning involved, and pacing of the bleep test. I wouldn't do too many though as the risk of injury is certainly higher, the last thing you need is to turn an ankle a week before the test.
I have also switched from using Runkeeper on the iphone to a Garmin watch and much prefer it. I think Runkeeper supports the importation of Garmin data (automatically in some cases in others you can export from Garmin Connect) so if you can still have your runs recorded within Runkeeper if thats a major issue for you.
Baggie, I got a 210 for Christmas and as far as I can see if you have the units based in miles then the autolap feature can only be set to .25, .5, .75, 1, 1.5, 2 and 3.1 miles. There doesn't seem to be an option to create a custom distance.