i am not concerned with it. i understand why you are but i think you are taking a bit too much of a fatal look at it.
i have a strong feeling that this iphone problem will be figured out by the time iOS5 hits (and/or it already has)- which will be in this month. i don't think the phoneguard software was designed for the limitations on the current iOS. this is just my hunch...
in regard to the battery issue- this is a challenge just like getting people aware of the product is a challenge. part of building a product is overcoming these challenges. i think in the short term the solution will be refinement of the current software to enable the product to run with periodic GPS check-ins rather than constant- AND people adjusting to a shorter battery life than they are currently used to.
long-term batteries will outlast the devices they support. here is an example of a company developing one variation of this tech on a larger scale: http://www.terrapower.com/home.aspx