Only phones running Android 1.6 or higher can run Searchify, so phones on Android 1.5 won’t be able to see it. The quick search box that Searchify enhances was only added in 1.6, so there’s no way the app can work on an earlier version.
Unfortunately this means that currently the HTC Hero won’t run Searchify. Apparently HTC are planning to release an update some time in March.