I have a Uwatec that I download to my Treo with their Aqua DiveLog software. It is very slick and works with an infrared transfer. It is a free download, so you might see if you can get it to work with a Vytec with some fiddeling.
Actually my Palm Treo 650 does not lose data (see above post) if there is a battery failure. A hard reboot will wipe data, but it is very rare you need to do this. If you have a GSM model (ATT, T-Mobile), much information is stored on the GSM chip. Also, if the unit is sync'ed, data will be backedup on your computer. I take several batteries on long trips and run them into the ground.