Jeroen, I also like Astromist, I tried out the beta on my Ipaq whent it was released and I quiet liked the features of it. There is another one that is now Free called Tachyon
http://tachyonweb.net/ you may want to look at this. It can also be run on the PC.
You may wish to review your thread title as this is what implies a comparison between AN and BETI. On its own BETI only offers a small fraction of the feature of AN. As it pretty much only tells you the encoder position. AN does a lot more. With PDA and Software at best it is an alternative. The cost comparison when you add encoders, cables, encoder mounting kit, PDA and Software you will find is not much.
Regards
Fahim