Ideas for paid app in multiple markets

I have a situation that I have not seen addressed elsewhere, so I'd like to ask folks for ideas. Here's what's up:

I sell a relatively expensive (US$25) app t开发者_运维问答hat I have sold for 10 years in various forms on different portable platforms. In general it's pretty vertical-market oriented (astronomers, ham radio operators) but in some cases is of general interest and has sold pretty steadily over the whole time it's been around. I have an Android version ready to publish but am not sure the best route to take.

The issues that are troublesome for me are that it must be possible to download a free, time-limited but full-featured version for evaluation, and that I need to be able to sell it to previous customers at half-price (just a long-standing policy of mine.)

Note that I am already set up to sell from my own website - have been doing it with other versions of the software for years, and the app is already set up to run in "trial mode" until a registration code is entered.

I have been assuming that I would publish it on the Android Market as a free app, and add code to it to look for an "unlock key" app that I would publish there as well. The idea being that a person could download and test the app, and if they chose to purchase it could either buy the unlock key via the market, or could go to my web site and purchase a registration code, allowing a path for my "customer loyalty" discount.

Unfortunately, I'm pretty sure this violates section 3.3 of the Developer Distribution Agreement: "All fees received by Developers for Products distributed via the Market must be processed by the Market's Payment Processor."

I have a couple of ideas, but I'd really like to hear some other opinions first. Sorry for the length - it's just a long question.

(Oh, and FYI, there is already a published iOS version of this app, and none of this is at all possible for it, and I think it's awful.)

You could get them to buy the app at full price and then send the discount back to them - like a cash-back scheme. It's not very efficient though.

1. You can use in-app billing to process the purchase. That way you won't violate any agreement.

2. You can publish more than one APK in the market, with different prices, and validate the install upon first run with a code you send them.