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RCCDroidPro https://play.google.com/store/apps/details?id=com.glensk.RCCDroidPro&hl=de
There is also a free version. I'm not sure about the limitations.
There's an app called rccdroid that I use for long exposures; it requires Android with USB host mode and a usb org cable, because it's wired control not Wi-Fi. It has a bulb button, but I've never tried it. I also use Time Lapse which works with Wi-Fi remote control.
Update the app on the camera. The preinstalled version is very basic, after updating you can control most things.
Edit: or you can use RCCDroid, but you have to tether the camera to the phone via USB. https://play.google.com/store/apps/details?id=com.glensk.RCCDroidPro