In search of a QWERTY Bluetooth keyboard that also works with the iPad 3 works and is not too expensive I went after some research to the HP webOS Bluetooth keyboardpushed. The keyboard is actually intended for the WebOS tablet "Touchpad" from HP, but thanks to Bluetooth it also works on other devices, for example the aforementioned iPad 3.
Unfortunately not all keys are supported, the triple assignment does not work under iOS or MacOS. For some characters you have to use the Apple pinout - e.g. AltGr + L for @ or AltGr + 5 or 6 for [ and ]. This is all you need to be able to quickly enter text on the iPad (this article is created with the HP WebOS keyboard on a 3rd generation iPad). Pairing was very easy: activate Bluetooth on the iPad, put the keyboard into pairing mode and enter the PIN that the iPad displays - done. If the keyboard is switched on, the iPad will automatically recognize it in the future and allow entries. Of the media buttons, the one for searching and the volume buttons work.
Besides the use on the iPad, the keyboard should also work on other devices that support Bluetooth, for example Android tablets. But also on MacBook or Windows PC (on the latter, the "Cards" key is the Windows key) you can use the little black one from HP - even if it can't replace a full keyboard.